To use images or not?
As the saying goes, a picture is worth a thousand words. Nothing could be more true when it comes to creating guides.
Your user base is likely broken up into people who like to read detail, vs those who prefer a diagram or video. Catering for both is your best bet, but you need to be careful that you don't go overboard with this. Adding in images for the sake of adding images will only overwhelm a user.
A correctly placed, helpful image though can mean the difference between someone understanding and moving on, or someone getting frustrated and giving up.
Adding images also makes it much easier for a user to browse an article, and jump directly to where they need to be since they can quickly see something similar to what they are looking for help on.
Apps for creating assets
For creating and annotating images:
For creating gifs:
For creating screencasts
Know of others? Let us know.