I am working with microRNA in Lupus samples and running qPCRs. I am currently using U6 as the internal control, and wondering if there are better controls to use because my data analysis is not producing the expected fold changes of expression
Using the small nuclear RNAs (U6 etc) are as suitable as using 18S for mRNA expression normalization as small nuclear RNAs are not in the same fraction as miRNAs. You should opt to use actual miRNAs that are expressed in your tissue type. I found that in my heart samples, U6 and RNU1a were unstable compared to candidate miRNAs.
If you're going to look at the genes listed by Benjamin as candidate reference genes, you may want to consider evaluating the stability of those genes algorithmically.
There are a couple good methods for this - GeNorm and Normfinder. GeNorm used to have a free add-on for Excel, but is now only available as past of the qbase+ software. However, Normfinder is free for academic use http://moma.dk/normfinder-software. These are useful if you decide to do a qPCR to evaluate multiple candidate reference genes at once, as these algorithms will try to determine the combination of reference genes with the best stability in your sample set.