Get on top of these easy jobs

You can quickly master these yourself, even if you’re not very handy. They’re all smallish jobs that can fend off big problems later.
Test your thermostat

Risk: If the temperature in your house isn’t what shows on the thermostat, your air conditioner or furnace could be working too hard.
How to DIY it: Every spring and autumn, tape a household thermometer on the wall next to the thermostat. After about 15 minutes, compare readings. If the difference between the two numbers is more than a few degrees, try recalibrating your thermostat (follow the manufacturer’s instructions).
While you’re at it: If you don’t have a programmable thermostat, consider getting one. An Energy Star–rated model can save you about $180 in heating and cooling costs each year. You can buy one for about $40 and install it yourself. It’s a relatively easy job; no rewiring required.
On the other hand, these are home improvement projects you should never, ever DIY.
Stop air leaks under doors

Risk: Cooling or heating the world outside your home is obviously wasteful – and expensive.
How to DIY it: Most door thresholds (also called a saddle; below) adjust up and down with screws. Turn all the screws equally until the door opens and closes without much drag and the draft is eliminated.
While you’re at it: You can seal drafty windows with removable caulk, which will keep cold air outside in winter and easily peel off come spring.
Watch out for more sneaky ways your home is draining your bank account.