Perhaps an ignorant question about weed...

I have another account on 2+2, but to be honest I'm a bit embaressed to ask questions like these, so forgive the new account, but OOT is usually good for a range of advice and opinions.

I recently started smoking pot -- not necessarily "regularly," since I can't really get it regularly, but once in a while. Sometimes I get stoned out of my head, and sometimes it's a very mild high. Sometimes it's me in the kitchen trying to figure out how to work the refirgerator, and sometimes it's more of a physical sensation. Sometimes time is completely screwed up in my mind, and sometimes things are fairly normal.

Why is this? I'll actually get different highs from the same batch, which seems odd.

Some possibilities:

1) I never smoked cigarettes, so this is really me learning to smoke for the first time. Perhaps I inhale deeper/differently at different times. I'm smoking out of a glass bowl.

2) Smoking a different part of the bud? I'm not really sure which part does what and where gets you high.

3) Different plants have different strengths?

I appreciate any comments or thoughts, as this is fairly new to me ...