If you are sure something will happen, use "when" instead of "if".

I thought of another tricky point which we should include in this discussion of conditional sentences. Sometimes we want to talk about a condition which we know will happen. In that case, you should use "when" instead of "if". "If" usually means that we aren't sure it will happen.

× If rainy season comes, I have to use the air conditioner to dry my house.
○ When rainy season comes, I have to use the air conditioner to dry my house.

× If it's been two minutes, take the noodles off the stove.
○ When it's been two minutes, take the noodles off the stove.

Both of these sentences are correct, but note the different meanings:

If you graduate, you will receive a degree. <- you may not graduate
When you graduate, you will receive a degree. <- you will definitely graduate

If you arrive at the station, we can go to the restaurant together. <- I don't know if you will arrive or not... maybe we aren't yet sure where to meet
When you arrive at the station, we can go to the restaurant together. <- We have plans, and I know you will come. I'll be waiting for you.

I was at Shiodome City Center this evening. When I'm there, I usually go to the soup restaurant "Chowders" to get a cup of garden vegetable soup. It's the only vegetarian soup on their menu, I think. The rest have some kind of animal-based bullion. However, today I noticed that a "taco rice" restaurant there has vegetarian-friendly taco rice! If I can remember next time, I'll order it.

By the way, "taco rice" is Japanese English. Native speakers can probably guess what it is, but I'd never heard of it before coming to Japan.
http://en.wikipedia.org/wiki/Taco_rice

When this laundry is done, I have to hang it. Before that, I want to eat a snack, so it's time to end this post. If you are tired of hearing about my laundry, please tell me!

Here's the whole list of posts about conditional sentences:
http://upgradeenglish.blogspot.com/2009/06/if-you-dont-understand-conditional.html
http://upgradeenglish.blogspot.com/2009/06/if-you-dont-get-to-station-before-last.html
http://upgradeenglish.blogspot.com/2009/06/if-you-put-hot-food-in-fridge-you-risk.html
http://upgradeenglish.blogspot.com/2009/06/if-i-dont-hang-this-laundry-tonight-it.html
http://upgradeenglish.blogspot.com/2009/06/if-i-were-empress-police-would-stop.html
http://upgradeenglish.blogspot.com/2009/06/if-i-had-stayed-out-bit-longer-this.html
http://upgradeenglish.blogspot.com/2009/06/if-you-arent-careful-you-might-make.html
http://upgradeenglish.blogspot.com/2009/06/what-would-you-have-chosen-as-your.html