I recently got myself some rhinestones for nail art and I am getting well into putting on the bling :) My old method was to use tweezers to apply the stones and just dropping them on. But then I watched the Konad video on nail art at www.konad.co.uk, and it says to use tooth pick dipped in clear top coat to pick up and put on the stones! Wow! Such a simple idea but it totally works! :)
I either stick my stones to the actual colour polish while its still wet, or I apply a little blob of top coat and stick the stone in there. Larger (2.5mm+ stones) need bigger blobs, and flowers and fimo will most likely need proper nail glue.
For rhinestones I also like to use two thick coats of Seche Vite/Poshe top coat as it secures the stones on the nail for at least 3 days. If you don't put on a thick clear top coat, your rhinestones are likely to come off within hours.