I think the Mayo clinic is a good place to go.
Generally, at least four of the eleven criteria of lupus from the American College of Rheumatology are usually present for lupus to be diagnosed.
1. Malar rash – a butterfly shaped rash across cheeks and nose
2. Skin rash – raised red patches
3. Photosensitivity – unusually strong reaction to sun light, causing a rash or flare
4. Mouth or nose ulcers – usually painless
5. Nonerosive arthritis – inflammation in two or more joints.
6. Cardio-pulmonary involvement – inflammation of the heart lining and/or lungs
7. Neurologic disorder – seizures and/or psychosis
8. Kidney disorder – increased protein or clumps of red cells in urine
9. Blood disorder – anemia caused by damaged red cells, low white cells or low platelet count
10. Immunological disorder – when your immune system attacks healthy cells
11. Antinuclear antibodies (ANA) – positive blood test not induced by drugs