AS a few have said, keep them upright for 2-3 days so that thencorks can properly seat themselves and after that if using most standard corks lay them down or upside down to keep the corks from drying out. NSWiner as made a statement here that all shoulkd know is controversial just like most things with wine making.
Sop far studies have shown that synthetic corks are no better then the cheapest standard coks and good corks are way better and that even screw tops are exceeding both. Me, I like a good mix of natural and synthetic and use Perfect agglomerate corks but Im pretty sure there is a little better quality out there and they are called 2 + 2 corks which are all natural in the middle with synthetic discs top and bottom.