If you have no opiate tolerance, take like 1 mg. No more than 2 mg.
Obviously, yes, you CaN take more but after 1-2 mg you flood your receptors. In the case of sub this is not a good thing because there are no receptors left open for the metabolite of bupe, which is norbuprenorphine and that is what gives you the opiate/full agonist feeling. That is why you hear with subs "less is more""
That is the very simplified version, but it should explain why with bupe it's not a good idea to keep taking more like it is with most other drugs.
Oh, and just put it under your tongue, let dissolve, don't swallow the saliva.