Few thing you can try. Start by making sure the car is in good mechanical shape (plugs, filter, etc). Inflating your tires to max sidewall pressures for less rolling resistance. You can go with a grill block. They are cheap to make and easy to install that will help the engine warm up faster. Look at your route and see if you can find another way that does not have as many stop signs etc. If you have flexibility leave earlier or later sometimes 30 minutes to an hour can make all the difference in the world.
Here's a thread on driving tips. As always the biggest improvement will be with driving techniques if you're not getting up to speed.
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