by lrt,take sri petaling line to bukit jalil and u will reach stadium within 5 minutes walk.
sales:better decide and buy on 1st-3rd day of the tournament,otherwise they might run out of size that fits u.
i never buy online ticket,so cant help.
If you are going for the Premier seats (with seat numbers), then buying online will be better as the good seats go first. Otherwise, you can buy on the spot. Go early, as there can be quite a queue at the ticket counters.
(I tried to buy Premier seats online for QF onwards, but the only seats left are on the side, so I decided to downgrade this year.)