Do you eat meat? If so, lean red meat is the best source. Having your meals with some Vitamin C (from fruit/veges) helps the absorption considerably.
I don't know how accurate it would be tracking it because a lot of foods have iron in them, but they aren't on the Nutrition Labels.
Below are a couple links which you may find helpful: www.mckinley.illinois.edu/handouts/dietary
I have had severe iron deficiency and it caused me to want to sleep all day, and when I would get up to walk anywhere in the house, I often blacked out. BUT having said that, tiredness can be caused by many MANY different factors - some medical and some just depending on what you have been doing. Even the change of season can cause it, so don't assume that if you are tired, it is because your iron is low! My suggestion is that if you are thinking of taking a supplement without first checking with your Dr and having your bloods done to see if you need them, then don't. Having too much iron can actually be dangerous.