Point of View

Point of view in technical writing of the "how to" variety should usually be second person. That's because you're telling readers how to do things, and second person allows you to speak in the imperative mood so often used for giving commands and suggestions.

Consistency is a hallmark of good writing. Pick one point of view and stay there. Here's an example showing how hard it can be to follow along when the point of view is mixed up:

Add oil to your car's engine by first opening the hood. Then I check the dipstick to see whether oil is needed. Pour some in if it's needed, and then Jonathan checks the dipstick again. I repeat the process of adding oil and checking the level until the dipstick reads full. Finally, the car starts and the oil light comes on and then goes off to indicate proper pressure in the system.

You can improve these instructions by rewriting consistently in the second person. For example:

Add oil to your car's engine by first opening the hood. Check the dipstick to see whether oil is needed. Pour some in if it's needed, and then check the dipstick again. Repeat the process of adding oil and checking the level until the dipstick reads full. Finally, start the car and watch to be sure the oil light comes on and then goes off to indicate proper pressure in the system.

See how these instructions speak directly to readers? Each sentence gives clear instruction that readers can follow at each step in the process. 

First and third person have their place and are useful for anecdotes and case studies. For example, you can lighten the mood in a technical book by telling a humorous story on yourself. First person is good for those:

Be careful which dipstick you pull and check. I once pulled the transmission oil dipstick. I kept adding engine oil and couldn't understand why the line on the dipstick never moved. Well, I did eventually understand after overfilling the oil pan and having to drain all the oil and begin over again.

Don't want to admit how badly you messed up? Blame it all on "a friend" instead. Third-person is the way to go then:

Be careful which dipstick you pull and check. A friend once pulled the transmission oil dipstick. He kept adding engine oil and couldn't understand why the line on the dipstick never moved. Well, he did eventually understand after overfilling the oil pan and having to drain all the oil and begin over again.

Taking a case study approach to instruction is helpful when you when you lack the knowledge or are otherwise unable to speak in general and authoritative terms. For example:

The way that I add oil to my engine is to first open the hood. Then I pull the dipstick and check the oil level. If oil is needed, I pour some in and check the dipstick again. I keep on adding oil and checking until the dipstick reads full. Then I start the engine and make sure the oil light cycles on and then off again to indicate full pressure in the system. 

This case-study approach allows me to say how I personally check my own oil in my own vehicle without my having to imply that my approach is the one, true approach. My claim is only about what works for me, and the reader must extrapolate from my experience to his own situation. 

Second person should be your default choice in writing instructional content. Choose second person, and stay in second person consistently except for anecdotes and case studies. Write those in first or third person as appropriate. Then move back to second person for your primary content.