i got bladder infection twice last year. doctor said that women have shorter urinary bladder than men, which makes women more likely to get infection.
so keep that area clean, use clean water (or toilet paper ? well, in my country we use water) to clean it up after peeing.
and also, some doctor said it as "honeymoon disease", because many women get this infection after having sex. it caused by bacteria which usually found in intestine. having sex can push bacteria up into the bladder through the urethra.
one thing more, remember to clean the area (when peeing) from front to back, to avoid bacteria spread to urethra.