thats some good advice there guys, i'll just emphasise a few points,
* how-to-paint guides are very handy when starting out, and occasionally later too. when you start experimenting with a new technique its always a good idea to read/see how others do first.
*
be patient. chances are when you try something new that it won't work right the first couple of times, and its all too easy to get frustrated and discouraged. if you feel youself getting angry at your paints walk away for a while, take a few deep breaths and come back in an hour or so with a clear head.
*paint carefully, don't just slop the paint on. be neat and tidy. this is an important lesson to learn at an early stage as it will become a good habit later. it helps to have a few decent brushes of various sizes for this, after all you can't paint details with a tank brush
*painting is a skill like any other. practice daily, even if its just for half an hour before work/school/whatever.
*get feedback from other painters. some people can be a bit harsh when giving c&c but others will do all they can to help you out. as ion raptor said avoid cmon for feedback, if they even bother to comment it won't usually be anything positive unless you're at their skill level. instead, bring your pics to us
we have a bunch of quality painters who
aren't full of themselves, so our comments will be the helpfull kind rather than the soul destroying "you suck" type.
thats all i can think of for now.