If you have just started on your tree, my advise (for what it is worth) would be NOT to start with someone in the 1700's that you know nothing about, but to start with YOU, then your parents, and work back one step at a time.
If you have a tree in front of you that someone else has done, then that will give you some leads - but make sure that the person who compiled it has verified everything as far as possible and not made assumptions. Check out where their information came from that went in to the tree - did they actually look at Parish registers? obtain certificates? check out censuses? If they didnt, then make sure you do. If they did, then make sure you know the source that info came from and that it had been checked personally as far as possible, before taking it as correct.
No point in you taking time and expense tearing across the couintry to go to a record office to look at a Parish regiser if someone else has already done it, but on the other hand very unwise to take someones word for it that x was born in y at z, if they havent checked it out.
