Reddit reviews Insulate and Weatherize: For Energy Efficiency at Home (Taunton's Build Like a Pro)

Get this book, Insulate and Weatherize (my library has a copy, check if yours does too if you don't want to buy it) and read about air-sealing. It is a good book for beginners and gives tips on where to focus your efforts.

I am in the process of air-sealing leaks in the basement (closed-cell spray foam) and ductwork (with duct mastic) based on what I learned from the book and instructional videos on Youtube and it is making a huge difference. In the spring I will focus on the attic.

I would strongly recommend you pick up a copy of Insulate and Weatherize by Bruce Harley. I got a copy from my local library.

I just finished reading through it, and even though I probably need to read it twice more, it's a great introduction to how insulation works and an awesome whole-house how-to guide on insulating and sealing.

Like other said, seal the attic before you insulate! Stopping airflow is more important than insulating, and insulation does not stop airflow.