if your wish has anything to do with controlling elements or vampires, then no
Aside from that, if you've no idea how to work a spell, then no spell will likely work for you. Learning to cast an effective spell takes time, study, and practice. Spellcraft is hard work - it requires a focused mind, and the will and ability to raise up your energy and channel it into the spell. In that, there are spells that you could use to help you reach your goals (be they humanly possible ones), but no spell will give you everything you want, nor will you likely receive instant gratification from a spell cast.
Spells are created by the witch for very specific purposes. So a spell that may have worked great for me may be of no use to you. I'm betting you and I wish for very different things :).
Personally, I think you may be able to wish for things that seem realisitic enough. You cannot wish to be a vampire or mermaid, those are friction and will most likely not work. Also, once you've cast the spell, you really shouldn't sit and wait for it to happen. I believe you must go and reach for it. The spellpossibly gives you more opportunities to grasp at it.