First, two amazingly important precursors:
"I can't find any mention of this in the memories!"
Chances are high that whatever you're thinking of has at least been mentioned, even if it hasn't been answered clearly. There's a thorough description right here about how to use the memories better, and how to make them work for you. Sometimes your question actually won't be in the memories, but these days that generally only happens with the advanced or bizarre questions.
"I'd like to know how to do this really specific effect."
Your very first recourse for understanding any one specific effect you see should be to ask the person who made the icon. In three years of heavy LiveJournal use I've yet to encounter someone who's unwilling to describe a particular technique or effect s/he used.
And now, for the most Frequently Asked Questions here in icon_tutorial:
1.) "My text is coming out too small, even when I set the point size to 200!" Alternatively, "My text is coming out way too big, even when I set it to 4 point!"
You need to fix the resolution of your image; it should always be at 72 pixels per inch. To find solutions to this problem, check the memories under text-related.
If you'd rather not search yourself, there's a guide for Photoshop users here; a similarly comprehensive guide for Paint Shop Pro users has yet to be posted but when one is, I will link it.
2.) "What are brushes, and how do I use them?"
Brushes are files of textures, patterns, or shapes of some kind that you can add to your images; you access them via a Brush Tool in your program. Paint Shop Pro and Photoshop each come with some brushes already programmed in; you can download countless more from various internet sites and LiveJournal communities (see #3). Brushwork has become very popular in LJ icons in the last few months, and when done well it can be a vital and exciting part of your image. (When done poorly it can cause madness in the viewer. I know, I've seen it.)
In the most basic sense, you use brushes by creating a new layer in your image, selecting your brush tool, and then clicking on your image. However, skillful brush technique takes practice. Many of the best brush tips are actually found in the full icon tutorials, though it will take some reading to find them.
For trouble with or questions regarding the downloading or installation of custom brushes, see the downloads and installations section of the memories. Posts archived there can tell you how to put brush sets onto your computer and then how to get them into Photoshop or PSP once they're on your computer.
The brushes section of the archive is a catchall for all brush-related posts. Several of the downloading and installation questions are cross-referenced here, as are suggestions of where to find certain brushes and brush types. Posts discussing tips and tricks for better brush use and creation are also archived here.
3.) "Can I use Photoshop brushes in PSP?"
The answer is, "sometimes." Whether or not you will be able to use a brush set that someone has made depends on what program he or she used to make the brushes, and what program and what version of that program you are using.
In many cases, the brush files themselves are not compatible with other programs. For example, brushes made in Photoshop 7 are not compatible with Paint Shop Pro 8. However, many brush makers make and include "image packs" with their brush sets, so that anyone using a different program from the one in which the brushes were created also can have access to them.
For some more specific answers:
Photoshop 7 brushes cannot be used in PSP8.
Photoshop 6 and below brushes can be used in PSP.
Photoshop brushes in PSP products: a summary.
A thorough and concise tutorial of brush basics, PS and PSP.
The posts and memories referenced above also include instructions on how to make brushes out of an image pack you've downloaded in PSP.
In addition, PS brushes are not necessarily compatible with all versions of Photoshop. There's a cutoff around version 6 or so, and therefore brushes made in, for example, Photoshop 7 won't work with Photoshop 5. (grass_stained adds, "It's the bane of my existence.") If you're using an older version of Photoshop, you, too will need to define your own brushes from a *.jpg image pack.
In fact, image packs are a pretty much universal answer to compatibility. No matter what program you're using, or what program the image pack was made in, you can use your image manipulation program to create your own brushes from an image pack someone has posted.
And this should be a lesson to all brush makers that image packs are an extremely useful and courteous thing to provide.
4.) "Where can I find a font [brush, screencapture, etc] that looks like this?"
The resources section of the memories contains posts that either have resources -- like brushes, fonts, etc -- in them or that link to sites that host such resources. In addition, the community's user info contains an excellent "links and resources" section, linking both to other LiveJournal communities and to websites that will be useful to you.
5.) "I can't get my animation to be under 40k! Help meeeee!"
The categories of the memories you want to check here are animation, movie icons, and saving icons.
Generally, you'll have to do one of three things: remove frames, make the whole image smaller, or reduce the quality of or the number of colors in the image. The specifics on how to do those things, and which would be the best tactic in your situation, are best found in the memories categories above, and may also be cross-listed in the ImageReady or Animation Shop categories.
6.) "Which is better, Paint Shop Pro (PSP) or Photoshop (PS), and where can I find them?"
For icon-making purposes, either will suit your needs completely. There are plenty of top tier icon-makers out there (and in here) using each.
Free trial downloads of each program are available on their respective developers' sites. For PSP, visit www.jasc.com; for PS, check www.adobe.com.
Photoshop is industry standard for professionals, in all fields, who need to do digital imagery work. However, for the home user or hobbyist, Paint Shop Pro is certainly sufficient. A copy of the latest version ov PSP will run you about $80 USD; the latest version of Photoshop is closer to $600. Browsing clearance sites, eBay, and the like can often reveal older versions of either program -- still 100% functional and generally just as good -- for much less.
A third program you may wish to inspect is GIMP. It's been slow to catch on, but it's a totally free (that's free, folks, $0 now, $0 later) graphics editing program that is comparable to Photoshop or PSP. Because many fewer people use GIMP than use PSP or PS, you may have a much harder time getting help with GIMP problems from this community; however, it comes with extensive help files, and its fan base is steadily increasing. Those who do use it recommend it highly. You can find out all about The GIMP project and software on their website, GIMP.org.
We cannot discuss illegal acquisition of these or any other programs in this community. Advocating the use of cracked software or 'warez,' or telling you where to find such things, is against the LiveJournal TOS and could get the whole community in a great deal of trouble. We can't tell you what you can or can't do in your own journal or on your own computer, but you cannot discuss it here. Posts and comments asking for or offering illegal software will be promptly deleted, possibly without warning. Please see this post for further details. I've never yet banned a single person from the community, but repeatedly advocating software cracks is the thing I can think of that would make me do it. So please, just don't.
7.) "I want to make it so you can see through my icon, you know? Like what's behind it?"
The effect you're describing is called "Transparency," because parts of your image are transparent. Easy, eh? :) The theory behind transparency is simple: you cut holes in your image, and then you save it in a file format that preserves transparencies (*.gif or *.png). The details can occasionally be more difficult.
For all the funny lines and hearts and things that you see on many transparent icons, the word you're looking for is "template," and the two go hand in hand.
The categories of the Memories that will be of the most help to you are the transparencies section and the templates section. And here are some things you may find in there:
Template tutorial, Photoshop
Template tutorial, PSP
And a few posts about saving images properly, so that their transparency and color information are preserved: one here, and some additional facts about *.png images here.
8.) "I've been looking at tutorials forever but I just don't get it! Can anyone help me?!"
If you find that you have trouble learning from tutorials, there are volunteers available who will be willing to talk you through a process or two, providing that you follow the rules and treat them courteously. Please see the Icon Tutors Project for further information about that.
Posting, "Can anyone help me? I don't get it!" to the community, without further elaboration, will incur the severe irritation of the moderators and will clog members' friends lists. Even if you are posting after being confused by something you already tried to use in the memories, please follow all of the posting rules in the community user info and make your post as thorough and descriptive as possible so that we can answer your question as clearly as possible, and hopefully improve the archive in the process.
Comments and feedback are welcome. If you have suggestions for questions that should be added to this reference, please comment, bearing in mind that the FAQ is only for those questions that appear frequently. Feel free to link to this post pretty much anywhere you feel like. And if you're trying to use the memories as suggested, and find some that are broken, deleted, or exceptionally useless, PLEASE keep a running list of the links to the posts and then let me know, either in a comment somewhere or an IM (contact info is on my profile). The archive of 700 memories (and growing) is too big for me to scan it with any regularity, but everything in there was read when I archived it and archived for a reason so I have some confidence in it. I'm happy to weed out the archive occasionally but I need everyone else to be my eyes and ears. Thank you. :)