Your wife could also try to use ovulation predictor kits. These help detect when she should ovulate, thus better increasing your chances. Now keep in mind, these tests only PREDICT when she should ovulate... they don't actually tell you that she did. To help figure out if she did ovulate you could have her do as the above poster mentioned... tracking her basal body temp (BBT). You body carries a fairly constant waking body temp. when a woman ovulates, her body releases progesterone which is a heat-emitting hormone. This hormone causes her waking body temp to rise. You can Google BBT for more detailed information. Using the ovulation tests in combo with tracking her BBT will help you not only predict when she should ovulate, but then will tell you if she acutally did. It will also help possibly identify a problem.
For example, my husband and I have been Trying to conceive and I was using ovulation predictor tests. I was always getting positive results but never ended up pregnant. So I started tracking my BBT as well, after about 4 months of tracking I realized that although I would always get a positive ovulation test, my temp wasn't always rising, thus I wasn't releasing an egg every month. I took this information to my OBGYN and she started me on Clomid (a hormone it induce ovulation).
The key here is narrowing down and figuring out when your wife ovulates. He is a site that can help her narrow down her window of fertility by using an ovulation calendar. American Pregnancy Association : Getting Pregnant: Ovulation Calendar
Also I highly suggest the book 'Taking Charge of Your Fertility' by Toni Weschler. I have it and it is a EXCELLENT resource! I got it on eBay for about $10.
Once you and your wife become familiar with tracking her cycle you could use a chart that I do, it makes everything easier to read and I took these charts into my OBGYN to show her my tracking. I used the "comment" field to write down the results of my ovulation tests. http://epigee.org/f/pdf/bbtchart_f.pdf
Once you have hit the year mark, your doctor will be willing to step in and try to help.