- Hold hits for 3-5 seconds.
- Do not eat or drink too much before or after you smoke.
- Minimum physical activity.
- Swallowing hits provides more of a body high that can last quite a while.
- Smoke a BLUNT. And not an ez-roll. A Honey or Grape Dutch.
- Conserve bud + space out smoking sessions.

While technically I follow almost none of these rules for keeping a nice high going, they do help. Regularly, I'll smoke a blunt, throw the roach weed in the bong, and chill for a while. Then I'll typically spring for some food. Lots of food and drink.
I'm also terrible at conserving my ganj, I typically will smoke quite a bit in one session.