Agree with catdaddy66, before I brew I read the instructions through two times. Then as I am brewing I am always reading ahead to make sure I am ready for each step on time. Cleaning and sanitizing is also very important, I probably spend more time cleaning and sanitizing than I do brewing. I learn a new lesson every time, here are the lessons learned thus far.
1. The amount of ice in your fridge will not be a sufficient ice bath. Go buy a big pack of ice from the grocery store before you start.
2. Make sure you have a way to plug up your sink for the ice bath.
3. You don't have to bring the beer up to exactly 5 gallons (as many recipes suggest), you can instead bring it up to a desired OG. My first beer came out really week (like 3% because I added too much water). With algebra you can figure out how much water to add. Say you have 3 gallons of wort that is 1.08 OG. You want an OG of 1.06. You want to know how much water (the gravity is going to be 1.00) to add. You can figure that out with the following equation. (1.08*3)+(1*x)=(1.06*(3+x)). Make sense? If not feel free to message me. I'll take an OG reading without adding any water, solve for X, then add that much water. I'll then take another OG reading which should in theory be the desired OG, usually it is very close.
4. Don't be afraid to transfer some of the "sludge", there is yeast in there. I was too cautious about this and think I lost the yeast by the time I bottled leading to a flat beer.