Don't expect all your produce to come from the CSA
Most CSAs do not provide families with enough fruit to meet their usual intake. Many don't provide any fruit at all, so it is good to ask what to expect in that regard. Depending on the size of your family and how much you cook, you will probably find that you need to supplement the vegetables as well, especially staples like onions, garlic, and carrots.

If you are not used to eating seasonally, do some research.
If you are not accustomed to eating seasonally, you may find that it takes a while to make a transition from eating whatever is at the grocery store (pretty much everything) to whatever is in your CSA basket (what's in season). It may surprise you to find that tomatoes do not ripen until August in your area. You should expect the season to start off lighter than it finishes. In most areas, the first crops will be salad greens, peas, green onions and the like. By the end of the season, the boxes should be much heavier, with things like winter squash, potatoes, tomatoes, and broccoli. Many farms provide a list of what produce to expect when. It's worth reading. If they don't offer you such a list, ask.

Quantity varies – good to ask up front.
When filling the weekly CSA baskets, farmers try and provide a variety of items, in a reasonable quantity. They don't want to be skimpy, and they don't want to overwhelm their members. Too much of even a good thing, and it ends up going to waste, which makes everyone feel bad. Over time, farmers develop a feel for how much is the right amount for their particular community – what's fair, what's reasonable, what will get eaten. Of course, the weather and other mitigating circumstances can get in the way of their ability to provide the ideal amount, as discussed above. One of the most important questions to ask before you sign up is, "About how much produce do you expect to deliver each week, and how does that vary from the beginning of the season to the end?"

If you want to preserve food for winter, ask.
Some farms allow members to get extra quantities of certain vegetables for canning or freezing. If this is something that interests you, talk to the farmer early in the season.

Make sure you understand the policies.
Farms differ in their policies regarding what happens with your box if you don't pick it up (e.g. vacation, something-came-up, I forgot, etc.) Make sure you know how these situations are dealt with, before the season starts. ------ from localharvest.org