For the sake of my tutorial I'm going to take an existing logo, this one. (click to download)

This was given to me in AI format. Load it into lightwave and you'll get a big error.

Why? It hasn't been saved in the right format and even if it did most of the time the paths are very 3D unfriendly you'll need to clean them up anyway.

Load it in Photoshop and define a really big size to rasterise, like 350 DPI or something. This is important for one of the steps later on.

Select the magic wand tool, set tolerance to one. Click on the brown contour and. Bam ! half of your work in photoshop is done.  Shift click on all the letters to get those as well.

If you haven't fiddled too much with the photoshop settings you'll see in the bottom right corner of your screen the layers panel and 2 other tabs, select the paths tab. and click the 'make work path from selection. This is why you need a large version of your logo. The larger your canvas size, the better this feature works!

Select file, export, paths to illustrator and save it in a sensible place.

That's it for photoshop.