how to concieve twins?

Im trying to concieve, and im praying and hoping for twins! Can anyone tell me any tips on how to boost my chances?

im 21 years old, iv had 1 previous pregnancy and i havent been taking birth control. I have been taking prenatal vitamins though, does that help? My son is 1 year old now.

Family history: my husband has twin brother and sister siblings, he is not a twin.

His dads side of the family has twins but i dont think there are any twins from my side.