Maria`s suggestions are very good
But if you have your stitches down (the most common ones are chains, slip stitches, single, halfdouble and double crochets) you can make anything you want. The most important thing now is practice. What ever you want to do, its important that your stitches are even, not too tight, not too loose.
I started with flowers. they are fairly easy and fast to make, and you get very different results depending on the yarn you use. It also helped me to learn to follow a pattern and count my stitches.
Oh and dont crochet in black at the beginning. it makes the stitches really hard to see (or maybe thats just me ^^)