'Hello,' she said, her Greek accent heavy.
There's quite a few threads around the place on this very topic, if you want to search Aspiring Writers. But I think the general consensus is usually, unless you are particularly good at it, to stick with some form of the above - maybe a little more subtle, though. Accents are hard to pull off well, and if they aren't, they are usually quite excruciatingly bad.
I'm sure others more knowledgeable than me will be along to expand rather soon, so I'll just leave you with a friendly welcome aboard!