Try to find out what all the features in Photoshop are for. Just start of with a blank canvas and try everything out.
Check out the pics of the others and study them,... try to think of a way they did their pics.
Keep on posting, you will learn from it. You will get better and better by it.
Always go for clean pics, work with paths and channels, use a lot of layers do adjusments can be done easily. Work with adjustment layers. Don't use filters too much for the effect only use them like a photographer would use his options in a dark room.
Have fun with it, maybe that's the best tip I can give you.
Good luck!
