Wages, facilities, location and club ambition are probably the key factors. However, managers influence can be important, but that is usually only through them previously playing under him.
We've definately got 3/4 of those and I presume we're not bad payers. We also had no trouble attracting good players when we were in League 1, but competition is far greater in the Championship. I shall try and keep the faith, but am getting twitchy. Our present team is good and we should still do well this season, but not many teams stick solely with previous team when they get promoted.