Two approaches, first the more usual one.
An overdrive pedal to the rhythm tone, and usually a bit more volume from the amp too (my amp has dual master volumes). I don't use a TON of gain, but usually I like a little more volume boost than what just the overdrive pedal gives me. A guitar lead is like the lead singer; it should be heard above everything else.
Second; make your rhythm tone with the volume rolled to 5-7. For leads, turn it up full. In this case too, I often use the second master volume too.
I like the first approach usually, as I like to have a tad more mids on my lead tone, as well as a bit more compression. But I don't want them on my rhythm tone all the time.
-Zaned