Finding People That Are Hard to Be Found Like Married People

I have just had a time with finding people that have changed their last name and have no trace..I have a friend that I knew when I was really young and we were stationed in the same place for about 2 years and I have lost touch with her and have been looking for her for a very long time..I hope that it isn't as hard as that to find my ancestors..I beleieve that everything has a purpose and that maybe one thing I will need to find out before I am done with my research..Both of my daughters were born from different fathers but they both have the same daddy.. I have a grandson that maybe interested in Geneaolgy too ..So I find myself wondering if I will be able to make the most out of what I find and what turns up..I have found out some stuff that was really cool..My grandmother had a brother named Walter which is what my husbands name is now ..Anyway Walter Cox which is my uncle married and had 2 daughters one Susan and the other Becky like me....Wow what a hoot...