It depends on when implantation occurs, which can happen anywhere from 7 - 12 dpo (i think). Some women swear that they had pregnancy symptoms as soon as 1-2 dpo, however hcg (the hormone that causes pregnancy symptoms) isn't produced until implantation occurs. So, if you implanted on 10 dpo, or so, then you would probably have enough hcg in your system to see symptoms 2-3 days after. So, in short, symptoms occur 2-3 days after implantation, generally. But every woman is different and will feel things differently at different stages.
The best is when you miss your period. it's depends on each individual woman.