Insect control is not as important in some situations as it is in others. An occasional cockroach can simply be squished; the odd ant will probably get out of your way on its own without a lot of commotion, and a spider or two can actually help control other insect populations. However, many common insects are associated with more than just looking gross; many insects are harmless in ones and twos, but can cause property damage or spread disease in larger populations. If you notice large numbers of a particular insect inside your house, it is generally a good idea to at least consult with a pro on whether or not this particular bug could present more than a casual nuisance.
Hiring an insect exterminator is certainly a good idea for problems that are out of control or for those who want to prevent problems in the future. However, while a professional is certainly the right person to call for well established insect infestation, there are several steps you can take yourself to reduce insect and rodent infestation during the early stages.
The wide array of pest control products available at your local hardware store (or even at your grocery store) can be very effective if used well.
Keep kitchens and other food-containing areas clean to discourage roaches, ants, and other insects.
Eliminating standing water is key in mosquito control (don’t forget to clean your gutters, as they make a great breeding ground when they are clogged).
Set traps in areas where they will do the most good. If you’ve seen insect activity focus on a particular area, that’s where you should focus, too.
Fill in and seal gaps where insects and small rodents can enter the house.
Make sure garbage cans seal tightly (and keep them sealed whenever possible).