How much should I increase my credit limit?

I have a credit limit of 500. Can I ask for a 1K increase or is that too much? I am applying online so I cannot know of an approval or decline quickly. Is there a guideline to go by on how much to increase your credit limit?|||It doesn't hurt to ask, in my opinion. On one or two occasions, I asked for more than they wanted to give and they met me somewhere in the middle. Most times I've made a reasonable request they give the whole thing, though. So I would go for it :)