The problems depend on the type of soil, your location, the garden's location, and the specific crop(s).

You've got to give more details if you want more helpful answers. Where about are you located (nothing specific, just a general location)? What type of soil do you have? How big do you want the garden? How much sun does it get? Is the area well drained? What do you plan on growing? Will you be starting from seed or buying transplants? Etc, etc, etc.

Rodney

P.S. There is a ton of information on the forum already that may be of interest.

Agree with Rodney that knowing your location or at least your garden zone is crucial. And we'd need much more detailed info from you to give you specifics but the majority of the posts already here are all about the problems many have encountered.

When you say "vegetable patch in my garden" what sort of gardening are you already doing - flowers, succulents, perennials, etc. as many things carry over from one type of gardening to another.

Dave

Also what type of pests you have in your area. We have zillions of gophers, so we have to do raised beds (for example)
Rabbits, gophers, voles, etc etc etc Nancy

Look into square foot gardening and/or EarthBoxes if you are just starting out. These are easy entry points into veggie gardening that are well documented and will get you hooked.

Here is one of my 4'x4' SFG beds that I planted out in early September. Bringing in excellent greens from it right now: