As an experiment, I didn't cut my hair after leaving the UK and riding through West Africa down to South Africa. By the time I reached Cape Town I looked pretty wild! Here's a photo of me before and after the first time I shaved my head. I've written this guide to demonstrate how easy and cheap it is.
With advice from a mate—Evan, a fellow baldy—I learnt to shave my head on a tight budget. Initially, I was reading guides online that recommended fancy, expensive products. However, I shave my head using cheap, disposable razors and soap. Triple-blade disposable razors allow a smoother shaving action and snag less than double- and single-blade. As for soap, just the cheapest bar you can find for washing your body.
Here's the steps I follow that demonstrate the simplicity of shaving your head with basic and budget products.
I'm an amateur so going slowly is crucial in preventing cuts. Good luck!