1. for new mappers, the most important thing to learn is simply what the editor can do. for instance, holding shift and dragging an object or group of objects will create a clone. a simple use for this would be to make a staircase by repeatedly cloning one of it's steps, a task that is somewhat more tedious when done the long way. learning the basics of hammer will save you time and effort for either indoor or outdoor maps.

2. your probably better aiming for smallish map. you're less likely to get bogged down with a small map, and would be more willing to abandon it if it went arse up for some reason. and as maps get bigger, there are more considerations that need to be taken into account.

3. that's the beauty of mapping

4. the tutorials here, or the forums for anything that you're not clear on.

Work on your mapping skill before you try and make something for the public.

I spent 3 years mapping before I made a single map, I went quite slow, but I think its better to learn the program and learn it well before you tackle the whole new world of playablity and online issues like lag and fps (though you should keep these things in mind).

Read all the tutorials you can and look at as many source maps as you can find. Also play HL2 and as many MODs as you can, I map my best when I am inspired. You should also watch a good deal of movies and go outside to places you would map (I was just in an abandoned asylum tonight).

"I think it's best for you to post these questions in the HL2 mapping forum. The general discussion forum is reserved for none mapping topics. "

My apologies. I read everything I could find and was confused actually. My take was:

"General Banter" General comments about anything.
"Maps" You can only post about a map you are already constructing, I have none.
"Art" Yeah right, my skill at map making can be called a lot of things but art doesn't head the list.
"Half-Life 2 editing" You can only ask one question per thread. I had multiple questions that weren't really specific to an editor. My questions centered more on the man, not the program.
"Half-Life" This thread seemed a bit old to me. However the same reasons applied as with the Half-Life 2 forum.
"Radiant editor" I have no clue what that is.

I decided to post here because it seemed the least wrong to do so. If its really bad, delete it and I will begin again in the forum of choice.

To the other less offended members, my gratitude mounts.

Finishing a project, teaches you far more than half finishing a 100. Also, learn the basics before you start mapping. If you want to practice gameplay FINISH an all orange map with fantastic gameplay. If you want to learn to make a good looking map. Load up Photoshop/Paint/Paintshop Pro/Painter/Pens and Markers/Paints and brushes and start drawings. 1 point perspective can be learned in a day. Just create great art. If you can make something look good with a pencil, you can make it look great on the computer. Best of all, you already know how to use a pencil, it'll take you a month or more to learn how to use hammer.

In all of my classes for Digital Art, we always started with a piece of paper and a pen. Reminds me of Dodge ball "If you can dodge a wrench, you can dodge a ball." No need to get all fancy with computer applications, use what you have lieing around that you are familiar with. No reason to complicate art by involving a computer while learning.