Can anybody tell me what to look for when picking a puppy. Not just its looks but in personality, they are only 3 1/2 weeks approx. Does it also matter what size they are....will the biggest pup grow to be the biggest dog?
Thankyou

Depends on a lot of things, particularly what you are wanting the puppy for and what breed it is. Personally, temperament is the most important thing for me. The first puppy to come to you is probably going to be the most troublesome!!! The one that cowers in a corner is probably always going to be shy (or maybe it just doesn't like you!). Quite often the puppy will pick you! If you're looking for one to show - you'd need to ask a breed expert.
If the breeder is experienced & you have faith in them (if not - why buy a puppy from them?), then their opinion is probably worth listening to, particularly if you've told them exactly what you expect from the puppy.
The biggest puppy won't necessarily be the biggest dog, altho' it does give some indication.