only way to build the tolerance is to eat spicy food. If you want to keep it up there, then you need to regularly eat that same level of spicy food until you're ready to take it to the next level. The fastest way to increase tolerance, is to eat something that is way beyond your capacity. It might suck for that 20-30 minutes afterwards but you will get over it quick. Everything you eat that you used to think was really hot, will have seemed tamed down and tolerable. If you don't like that idea....slow and steady wins the race.
I started out eating Pico de guillo at the beginning of my spicy career. I moved up to making home made fresh jalapeno poppers. (De-seeding them not even knowing about where the most heat came from yet...lol) That used to burn me up bad back in the day. Then I moved to the trusty old habanero....this sucker really ramps up the taste buds ability to handle anything underneath it on the heat scale. I grew my first plant and just started using them in my cooking from time to time. I took a long break from most hot stuff for a while for no apparent reason. I then started up again (for no apparent reason...hahaha) I started searching online about hot sauces and found this site (among other unmentionables) Then I found Maria's Naga Jolokia hot sauce and that took me to a whole new level. After I finished a few bottles of that, I had joined this site and bought my first box of super hot peppers.....The rest is history my friend.