Many women can and do conceive in their forties. Many of them tried for longer than their 20 year-old counterparts and took great care to do everything the "right way", including folic acid and ovulation tests. Some of them had to have IVF or other fertility treatment to realize their dream of getting pregnant. Others got pregnant by surprise, with no effort at all.
It is true that your objective chance of getting pregnant after 40 is less during every menstrual cycle, but that doesn't mean that you can't get pregnant. Technically speaking, you have a chance of getting pregnant naturally as long as you haven't entered the menopause yet, something that can happen after 50!
You can help your chances a little (or a lot!) by living a healthy lifestyle. You may want to go for a general medical checkup with your doctor before trying to conceive, to make sure you don't have any vitamin and mineral deficiencies and that you are generally healthy.
The same goes for your partner. You can also use ovulation tests to determine when you are actually fertile. Making sure you do the deed on the right days really does increase your chances of having a positive pregnant test that month a lot! And, if you have been trying to conceive for more than one year, you can see your doctor again to discuss artificial reproductive methods.