Some things that are useful to know about a festival:

Where is it, when is it, how long has it been going, and is it particularly geared to some particular type of music?

Is there a season ticket etc?

How spread out are the venues? (ie, can you walk betwween them)

Is it in a town/village, or in a field on its own?

Are there informal tune sessions?

Are there informal singarounds?

Are there storytelling sessions?

Any competitions?

Is busking allowed/encouraged/discouraged?

What are the arrangemnetas for ensuring children of different age groups enjoy themselves?

What's it like for people who can't walk, and so forth? Noy t just access to venues - steep hills are also worth knowing aboutr. For example Whitby.

Camping? And how far is this from events? And is there a festival bus service if it's a long way?

That'll do for a start.