If you want them straight, use a stake at either end of the row, with twine to help you mark them for the hoe. I do beds for all of the crops that it makes sense to do that way: greens, smaller plants, onions, etc. Corn, and potatoes are in an intensively spaced area. Corn, I do sets of 2 rows 12 - 18" apart, with each set of rows 2 - 3' apart. Potatoes, I always plant them so I can reach to the middle of the bed from either side to deal with potato bugs. Then there are the sprawlers, and the things that need to be trellised... so there's very little in my garden that gets planted in an actual row.
