My fav way.
Find a populated area with 3 or more Pokestops close to each other.
The more cellular activity around you, the more Pokemon will spawn, so make sure there are other people around.
Pop a lucky egg and modules on the Pokestops and enjoy a constant stream of Pokemon spawns.
Grab the Pokestops every 5 mins and catch everything that spawns.
Evolutions
Catch as many 12 candy evolution pokemon as you can. (Pidgeys, Caterpies, and Weedles.) - Pop a lucky egg and get in as many evolutions as you can. The evolution animation takes ~40 seconds. So you can usually get in about 30-50 evolutions in 1 lucky egg use. Its 1000 exp per evolution and you can do this at home before bed, just save your catches from throughout the day.
General leveling tips
- Catch everything you see, even if you just xfer it after
- Open every Pokestop you come across, even if your bags are full
- Spend your pokecoins on lucky eggs