Apparently even some really educated people are unsure of how to vote at the coming elections, so I was privy to a small explanation that went something like this.
If there are 5 candidates they'll be listed as follows:
If you're voting for only one candidate simply put an 'X' next to their name. If you are however going to do preferential votes then you need to stick to numbers. So '1' next to the guy you really want to vote for and then '2' and '3' next to your second and third choices respectively. You can't put a X and numbers or your vote becomes invalid.
This is so that if there is no clear winner preference votes will be added to the last two standing. However apparently preferential votes have never been used in an election in Sri Lanka with the winner always being quite clear cut.
Another obvious one is not to write anything on your voting card like comments on the candidates. This will also invalidate your vote. Apparently this is also done sometimes but probably not by the English speaking crowd.
Happy Voting (assuming you are actually voting)