[Alkaline]

Multiple number of outs by 2 and add 2. So 9x2+2=20. 20% chance of making your flush with one card to come. So you should call about a bet about 20% of the pot. Thats with one card to come. A lot of people will call pre turn and when their card doesn't come they fold before the river. Also read what Pants said. He put some good stuff in there.