I've just started to play Pirc Defence.Can Pirc players give me any strategical/tactical tip?

you can also use the a6 -> b5 plan. i do.

Is it 6. ...a6 instead of 6. ...c6?

depends. sometimes i delay castling for a long while.

can you post an example game or line to show me some basic startegies of pirc?

a good thing with the pirc is that most of the moves can be made in any order!not all but alot of them. and the first 9 moves or so are generally the same, maybe in different order.I think its a solid defense for black!

This opening is played by the group 1...g6 Modern Defence Playing vote chess with that team is one good way to learn the pirc

I used to play it all the time...I felt that it was best for black to try and keep the position closed because I noticed that development advantage (which white has) is less likely to result in immediate disaster in a closed position.

Later I also realized, however, that if black forces things to stay closed, he can wind up very cramped and inflexible..white can use his first move advantage to take and hold on to critical squares. It can be very hard for black to scare up counterplay, so white can be somewhat insolent about his moves and even get away with it.

I also played the a6 stuff as black, after some experience with it and some investigation in other openings I decided that it actually might be better to use this plan in a philidor, seemed like a more accurate move order.

I remember a lot of basic concepts of the pirc, but I try to play very open defenses as black now, where counterplay can be more immediate, where its easier to force important exchanges, and I can make better use of accurate calculation.

I play the Modern (1...g6 with the idea of delaying ...Nf6) now because it's a tad more sharp imo. It's plenty more dangerous though... Anyway, a good rule of thumb is to not let the pawn structure get symmetrical. If that happens then White can just sit there and slowly take up more and more space while you sit there and shift your knights around.

Lev Alburt's book on the Pirc was somewhat of a disappointment because he gave a lot of positions where Black had no play at all. He didn't like the dangerous ...c6 or ...a6 lines but when you don't play that stuff then don't expect anything but a drawn out game where you don't get to do anything. His answer to the Nf3 stuff was pretty much "draw" but who plays the Pirc for that?

"P.S. never put a pawn on c6 it takes the square from the knight"

Sorry no, that's bad advice. In fact, one of the mainlines of the Classical Pirc goes 1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.Nf3 Bg7 5.Be2 O-O 6.O-O c6

Actually, as OP posted a line of the classical variation, I have a question here too: For some reason I can't make up my mind about what would be the best sixth move for Black to play here. Book moves are:

6... c6

6... Bg4

6... Nc6

6...a6

6...e6

I vaguely tend to favor 6...c6, but I also find 6... Bg4 very natural and 6...Nc6 nicely provocative. I'm not very much into the "Modern" 6...a6 stuff and the fashionable Hippopotamus 6... e6. But what do you guys think?