I'd expect this to be obvious but I've seen quite a few resumes for people applying to where I work over the past few weeks and some of them are just terrible. Make sure the layout is clear and that education and work experience you have are obvious and go into a bit of detail about what they involved. Spell check and get someone else (or several someones) to read through it as well. Also, read the adverts and refer to key points in your covering letter.

If you're going for programming/computery jobs then I have more advice but otherwise that's all I can think of right now