What suggestions do you have for better e-learning surveys?

Our ID team is in the process of developing a standard survey for online training at a healthcare organization which will be completed mostly by staff. What suggestions do you have based on your experiences in making the survey more effective?

I am specifically interested in suggestions for the following:

-Average number of questions

-Number of choices for rating responses

-Typical kinds of questions for Level 1 evaluation 

-Do you find that including a neutral rating increases the chances of it being overused?

-Do you find that respondents make use of the optional text-entry fields to add an explanation of their ratings? Is it better to add this after each question or as a stand-alone question for additional comments?

-What tools do you find work best in collecting this information while still allowing for a high rate of completion? We use SL2 with a custom-built LMS but its survey tools and reporting capabilities are not very robust.

Thanks in advance for your insights.