How do I start?

I am wanting to map, it looks cool making your own world. Can anyone forward me to a good way to learn or teach me some things? ( making maps for garry’s mod mostly) I have no idea how to open hammer, I don’t own CSS or HL2 so I don’t know if that will be a set back but I need help formatting hammer for it to work how it is supposed to and stuff like that!

that video will cause you problems you don’t use source sdk because its out dated If you have Garrysmod and it works go to the garysmod Bin folder in there you will see Hammer.exe click on and Hammer will open
then reading links 1 -10 you learn how to build your 1st level once you have that mastered it just a case of practice,practice and more practice building bigger maps as you go

THW has been indispensable in teaching me how to work the trickier parts of hammer, so after going through YFM on Valve’s page, give his tutorial series a run:

It also helps to get a mapping buddy that doesn’t mind helping you out when you really get stuck.

My friends aren’t interested in making things they just like to play on things that others make (trying not to make this sound sexual)

Thank you all for the links and advice