I think that almost every country with a code-editing body should provide you standardized test methods for measuring creep and shrinkage of concrete. I'm very sure that you find an associated BS, too.
In any case, consider that you should not measure creep only but also shrinkage as these two interact. If you measure creep only, you will definitely overestimate it (as the specimen shrink, too, in the same time). Also note that these tests ususally take a year (that is what is prescribed in Switzerland, at least) - so start early!
a constant stress equal to a fraction of the compressive strength (30%, 40% or 50% depending on your goal and applied code) will be applied on the series of vertically set up of concrete samples (2 or 3 cylinder in each creep rig)
the strain behaviour under constant stress will be recorded automatically.