Does your camera actually incorporate a rangefinder as a focusing aid, or are you using a camera where you have to just set the focus distance, based on estimates?

If it does incorporate a rangefinder focusing aid, is it separate or coupled to the focus of the camera?

If you have a coupled (or uncoupled) rangefinder, I'd suggest checking it's accuracy against a useful target (a long picket fence shot at an angle is a good choice - don't forget a tripod and a tape measure).

If you don't have any focus aids, and are basing your focussing on estimates:

1) consider obtaining an accessory rangefinder focussing aid; and
2) combine hyperfocal focussing with practice at estimating distances - i.e. leave the camera set at the hyperfocal distance, but adjust based on estimates at the time of exposure; and
3) make sure that you are able to work at smaller apertures, to take advantage of as much depth of field as you can.

Hope this helps