If you choose to go tanning please stop 3 days prior in case you burn.
If you are just going to be outside in the sun naturally, be mindful of tan lines especially if your dress is strapless.
If you choose to do a spray tan test out the place/formula 3 months prior to see how it affects your skin and the color.

Get in good skincare habits before the wedding at least 6 months prior so your skin is in a regimen by then. I highly recommend and use myself MAC volcanic ash exfoliator. It is amazing and works on all skin types!