Try to avoid standing for too long, and don’t lie on your back after the first half of your pregnancy.
Make sure you’re eating healthily, and keeping your blood sugar levels up, and that you’re drinking enough water. Dehydration and overheating can cause dizziness even when you’re not pregnant, so be extra careful.
In most cases, dizziness is a completely harmless side effect of pregnancy. However, if your dizziness is accompanied by bleeding, or pain, you should talk to your doctor immediately. This is often an indication of an ectopic pregnancy. Ditto if you actually faint – there may be something more serious to worry about!
Other than that, deal with dizziness by sitting down when you start to feel light headed, and try drinking a glass of water to rehydrate yourself.