Keep it Simple
Any questionnaire you design has to be one that people are willing to answer. The main point is to make participation easy and inviting. If it's too complex or time-consuming, the recipient may throw it away.
Ask questions that call for a check mark in a list of alternative answers, a simple yes or no, or one word (at the most, just a few). As you write each question, check carefully for how well it fits your stated purpose. Check for ambiguity and whether they will elicit the kind of responses for which you are looking. It's a good idea to ask for just one piece of information per question.