Steam is really the best way to get it, but if not, check to see if you can buy HL:2 boxed. HL2 comes with Counter-strike: Source.
1.6 was good in its heydey, but Source is really the way to go, especially if you're new to CS. The only people who still play 1.6 are steam haters, hardcore pros, people in China, and people who hate new technology.
Source has nicer graphics, a tad-bit more forgiveable aiming, and much greater customization options.