Green Thumb?

I am going to try my hand at gardening this year. My sis in law, Jenn, has offered to let me plant a small garden in her backyard, so I think I'm going to take her up on that offer. I've never really done anything like this. Well, I had to weed our garden when I was a kid but let's face it, weeding is a whole different world than planting and caring for a garden. So, since I am so new, I would like to know if any of you have any tips or advice you would be willing to share. I'm desperate, really. I found this website that gave some good advice, and this is what I found out:

On the north side of the garden, it's best to plant tall things like corn, peas, and beans.
In the center, plane your mid size crops such as squash and tomatoes.
On the south side, plant your low lying crops like carrots, lettuce, and onions.

It is best to have your rows run south to north.

Companion planting: It's best to keep some plants away from others.
Carrots love lettuce, onions, and tomatoes.
Corn loves peas, cucumbers, and potatoes. It hates tomatoes.
Cucumbers love corn, sunflowers, but dislike potatoes.
Lettuce loves onions, strawberries, carrots, and cucumbers.
Onions love lettuce, strawberries, and tomatoes, but hate peas.
Tomatoes love carrots and onions.
Beans and onions need to be kept far apart.

This year I would like to plant: asparagus, carrots, corn, lettuce, peas, cherry tomatoes, zucchini, onions, potatoes, and some herbs (don't know what kind yet).

What about fruit? What kinds can you plant? Can you plant watermelon and canteloupe?

I also heard that you should plant some flowers.... I can't remember why.

So, as you can all clearly see, this will be a challenge for me. But I'm up to it. I would also like to do some canning later on this year. I think I'll start with the garden for now. So bring on the advice and tips!!!!!