Just over a week ago, I replaced the rear brake pads on my bike and, for most of the intervening time, you would have heard me coming if I had cause to brake within earshot of you. That was because the previous pads were quite worn and, when I put the new ones on, I left them ‘toe out’ rather than ‘toe in’.
You can find technical details, including diagrams, on other sites. What it boils down to is that you should set the pads so that the front edge is a little closer to the rim than the rear edge. I found various theories when I was looking it up this past weekend (including some who claim it is a waste of time) but my subsequent adjustments meant that I eliminated unwanted squeaks from my rides to and from work yesterday. The brakes also felt that they were performing better too, so a win all round.
The front ones will need doing soon (spare pads already on hand) and, this time, I should get the toe-in right from the get go.