hi flower, there are lots of things that affect fertility.
so for example age (of both parents), weight(under and over), smoking and drinking, diet, exercise
have you thought about the obvious of doing more sex? There's only about 24 hours every cycle when the egg could be fertilized (identifying the days you are ovulating and doing it on thise days can help) Many ways of doing this , ie taking temp daily, examining cervical mucous consistency, using a fertility monitor or ovulation sticks.
They also say lying on you back with a pillow under your bum after sex helps (because gravity aids the sperm getting to the right place) dont get up and wipe after sex, don't go and have a wee. Some people say "concieve plus" helps (although i am dubious) some people say acupuncture can help. How long have you been trying for? If it's been 18 months-2 years it may be worth going to the GP