I find that you have to do a bit of everything. Leaflet drops work well for me, in specific, targeted areas. We also try and keep our Facebook up to date and relevant.
Do you ask clients how they found you? I'm surprised how many say 'Google', so a good website is a must. We run an ad in a local weekly mag. We do it every month. It really isn't cheap, but the repetitiveness gets your name out there.
Finally, when we're busy, I always have to remind myself to advertise. It's easy during a busy spell to become complacent!
Vic x