The biggest tip I can give, is don't run before you can walk.
Attempting spell casting or other forms of magickal practice without truly understanding and knowing what they are doing can undermine your magickal practice for the future. Mainly because without the knowledge to undertake a successful magickal workings, it is almost guaranteed that it won't succeed which can sway your belief that it can work at all.
Study, and study some more, if you can get your hands on pdf's, forums or books, the more you read and study the better before you begin practicing spells.
Once you start casting, don't get disheartened if they don't work instantly, it can take: Days, weeks, months, sometimes even years before you can see results from a spell and sometimes they don't work at all because it isn't the right time for them to work. Don't give up because you don't see results right away.