The folks over at the Center on Regulations and Markets at Brookings have written a handy and short (seven pages!) guide to commenting on regulations. It discusses the federal rulemaking process; how to structure a comment letter; some things to consider about a regulation; assessing the legality of a regulation; and the mechanics of commenting on the rulemaking process.
If you’re interested in writing effective comments to HUD (or any other federal agency), this may be a good guide to take a look at.
The guide can be found here.