Dev,
For coriander, did you crush (break the seeds into two) the seeds a bit before putting in the pot? If you don't it won't come.
Mint is easy to grow, specially in Singapore, you can actually remove most of the leaves from the stem when you buy some for regular cooking and stick it in a pot and it comes out quiet well.
Leave your plants where they can get sunlight. And keep turning the pots once in a while to avoid plants growing in one direction.
As for differnt types of mint, I heard that some types of mint can actually cause miscarriage, don't remember which ones though!
thanks