Tutorials on topic models and LDA
If you're working in R, Carson Sievert's tutorial on using LDA to model topics in movie reviews is an excellent starting point:  

http://cpsievert.github.io/LDAvis/reviews/reviews.html

This tutorial makes use of LDAvis, an interactive visualization of topic and word distributions that can really aid intuition.

Also, although not short, David M. Blei's lectures on topic models are a great resource for understanding the meaning behind the parameters: http://videolectures.net/mlss09uk_blei_tm/