If you ask five headshavers, you will get 5 different responses. So I will give you what I find works best for me.
First, before you shave, you should use clippers and buzz you hair down as close as possible. No razor work well if you still have hair over 1 or 2 mm in length.
I shave in the shower so I have plenty of steam and moisture. I use an anti-fog shower mirror. Foe a first shave, I would do it in front of you sink with a larger mirror. Also, expect to need 20 to 30 minutes your first time.
I start with a cleansing apricot face scrub on my head, and then rinse that off.
I then lather up with Cremo brand shave cream.
I shave against the grain - you may want to start with the grain for the first time and until you know how you skin reacts to being shaved. If you have sensitive skin, shaving against the grain may cause some irritation. SI my description will be against the grain, just reverse the direction for shaving with the grain.
I use a Gillette Fusion cartridge razor. I start on the top of my head on one side, and shave from front to back. Jus let the razor glide across the skin, no extra pressure required. Each stroke of the razor I move over about 1/2 the width of the razor. Rinse the razor under hot water every 2 to 4 strokes.
Once I reach the opposite side, I then start at the front on one side, shaving from bottom up, just past the section already shaved on top. Again, I move the razor over about 1/2 the width of the razor, continuing all the way around the back and to the opposite side.
Once finished, with wet hands, I rub my head feeling for areas that may have been missed. If found, I follow with a stroke of the razor to get the section missed.
Caution: We all have some difficult areas where it is difficult to get smooth. Don't continue with multiple passes in one place, or you will get razor burn.
Good luck, I hope this helps. Post a photo of your results and let us know how it went.