is this Mitzvot only going to be practiced in the future or are some people doing this today?
(is this just like donating to your Synagogue?)
Do you get to pick which Kohanim you want your tithes to go to?
Or will they be seen as divinely appointed so that it won't make a difference?
Hi MakaB,
First of all, generally what we call "tithing" is the 10% amount which goes to the Levite (Leviim) not the Kohanim.
I think you are referring to the "Teruma" which is a portion of your produce that doesn't have a set percentage amount (except for those suggested by the Rabbis).
Biblically this practice of giving Teruma only applies in Israel. It would be practiced today, but the problem is we are not able to prove who is a genuine Kohen for them to be BIBLICALLY established as such. (for other purposes, we are satisfied with a 3 generation proof e.g. Aliyot etc.-but here we need a direct line)
For that reason, ppl. today take part of their produce and burn it, because if we can't give it to a proper Kohen you at least must make sure you don't benefit from it.
We have the same problem when it comes to taking Challah from our dough. We wind up burning it, though ideally it should go to a genuine Kohen.
When Moshiach (the Messiah) comes (may it be very soon) we'll figure out who is a real Kohen and reestablish this practice as it was done back then.
And yes, you can choose which Kohen you want to give to. Absolutely, that' you're right.