Keep your hands at the brakes
If you are in a group ride you often need to brake a bit. Whenever possible, do not brake too hard, because braking hard will get those riding behind you into trouble very soon because of the ‘accordion’ effect. If you brake a fraction too late, you are usually able to brake in time, but your brake action will be sharper. As a result, the people behind you will have less time to react. They must in turn then brake even sharper. And so on. Until someone hits the rear wheel of the rider in front of him/her….
If everyone keeps his hands on the handle bars, then the corrections needed will be less and the movements of the group as a whole becomes much quieter. That is why you always have to have your hands at the brakes. That saves response time if you need to brake. Useful for yourself and especially to those who ride behind you.
Your reaction time in meters
Suppose you ride with your hands on the bars and something happens in the group. Suppose that it takes you a second to hit your brakes in that position. If you ride at 30 km/h, it means that you only start to brake after 8.33 meter. Pretty late if you riding close behind one another in a group. The difference with a normal response time is soon a few meters.
Technique of breaking
The largest braking force comes from the front brake. If you brake there is much more pressure on the front wheel than on the rear wheel. The front wheel therefore has more friction with the road. So more braking power. The rear wheel has a lot less pressure on the road and slips earlier. By the way, you’d rather have your rear wheel slip than your front wheel. You can do something about a rear wheel slip. Namely: release the brake. Then the bike straightens itself again. A front wheel slip can hardly be repaired. You have to prevent that.
See also Specials: Crashes, the near fall of Fuglsang Crashes
So: You brake when you (still) drive in a straight line, for example before a turn, a lot and hard with the front brake and less with the rear brake. If you need to brake in the corner, do so carefully with the rear brake. Make sure you have the correct brake pads and that the brakes are properly adjusted. In particular, you want to prevent ‘biting’ and getting into the slip.
See also Specials / cycling in mountains: Equipment
Another thing is of course looking and anticipating and therefore having more time to respond.
See also Riding in groups, looking ahead: Anticipating and making changes slowly.