There are several considerations to a veggie garden. You'll need to consider:
- Your geographic region/zone
- What veggies you like to eat
- How much space you have
- How much time you have to devote to it
- Whether you want to grow from seeds or seedlings
- What kind of soil you have OR how much you can spend to improve/replace it
Your zone determines what will grow where you are. Some things will grow almost anywhere, while others are very picky. Check with your local feed store or nursery if you're not sure. They will almost never carry anything that can't be successfully grown locally unless it's an exotic that would only be grown indoors.
What veggies you like is probably one of the most important things to think about. The first time I had a garden I bought seeds for everything under the sun, including stuff I don't eat and don't even know anyone I could give it to. These days I grow tomatoes, cucumbers, green onions, green beans, strawberries, and occasionally, potatoes. I also do lettuces sometimes and I'll be doing some variety of peppers this year, I think.
My gardens are Square Foot Gardens. I have two that are 4' x 2', and one that is 16' x 1'. I plan to put peppers in boxes or pots separate from the rest, so that the flavors don't cross. I also put lettuces in pots when I do them, because they don't like the same conditions the rest of my veggies like. Using the SFG method means that the soil in the yard doesn't matter. I've built raised beds, and mixed up the custom soil mixture that I need. I have a stack of tires for growing my potatoes in, when I think to get them in (I didn't this year).
I don't have a lot of time to weed and give the garden the attention I'd like to, and that's where SFG methods help, too. I put down weed blocking sheeting when I built my gardens, which helps cut down on weeds. I plant my plants closer together, which also helps prevent weeds. I use companion plants to help keep veggies healthy (marigolds, for example). This way, the weeds and critters don't get too far out of hand between weekends.
I was very gung ho for my first garden, and started everything from seed. Some worked well, some did not. I made many mistakes that first year, so it's very hard to say whether starting from seed was one of them. I did enjoy watching them sprout and grow, though. If you want to start from seeds, you need to start earlier in the year, and usually indoors. In recent years, I've bought seedlings for most things from local farmers. That way I know where they've come from, and how well the previous lines of those seedlings have produced. Probably more important, though, if I'm honest, is that by buying seedlings, all I have to do is get them in the ground on time, water, weed, and harvest. I don't have to go back and thin back extra plants.
One other thing to consider on the amount of space you have is this: you can grow enough veggies for yourself and a small family all summer in very little space. You need good lighting - most vegetables are sun loving, and want 6-8 hours of full sun a day - but not that much space. If you have a porch that gets that much sun, you can grow veggies in pots on your porch.
Finally, get to know someone at a local greenhouse or nursery, or a local gardener. These folks usually love to talk about gardening, and they're an invaluable source of information, assistance, and sometimes seeds or seedlings. My first year, I had a ton of help from a neighbor, including his offer to plow up my garden plot with a cultivator, and getting a few tomato seedlings from him, along with a lot of great advice.