[Hatorade]

When I was new to hammer I started my levels in a corner and built outward. That caused a lot of fucking headaches. Some tips from a self teacher:

Start with a HUGE HUGE skybox. More then you think you will need a lot more. Get it perfect use 45 degree angle cuts and all that save it and never save over it. This will help later when you make more then one map. Start in the upper middle/center of the skybox and work outwards. A building or some type prefab will help you scale the rest of the map. Make a flat boring ground brush and texture it. That will help in placement of everything. You can put it above or below the current ground and move that ground later to fit your structures and all that. Build walls and boundries at the very end. Also don't build a square map go for octgon at the oddest. U shapped maps automatically give you 1 choke point 2 if you want some way to connect the U across the top or whatever.

Learn all the little hotkeys and shortcuts. Like how to auto aline 2 textures or how to make textures fit the size of the brush. I forget the command off hand but they speed things up greatly.

Lighting is also really important if you have a lot of indoor areas.

Wing it, some of my best maps were me just building areas and putting them together to make one map. Sure you can draw and graph it out but you can't really do that until you have made a few maps using hammer. If something is frustrating or you can't get it how you want. Leave it and move on to another area. By the time you come back to it you will figure it out or have a better idea.

The tools can do anything you can think of you just don't know it. Google it or whatever and you will find your answer.