The Weightlifting Plateau - Causes and Fixes

Cause 1: You are overtrained, and your body is no longer healing properly 

Fix: Take a week off. In general, you should take a week  off at least every 12 weeks.

Cause 2: You have a mental block which is preventing further progress

Fix: Try visualizing yourself completing the lift successfully, prior to the attempt.

Cause 3:  You have a lagging body part. 

Fix: Prioritize that body part in your split. You can do this by putting exercises for it first on a given day, or by having two days that work that muscle per week. 

As an example, if you have weak triceps, your bench press may stop progressing, due to early fatigue of the triceps. In this case, you would want to do isolation work for the triceps, either on a different day from your bench press, or prior to your bench press.

Cause 4: Increments of weights are too high (eg. more than 2.5% to 5%)

Fix: Make yourself some microloading chains - see the method here. 

General Fix 

If these tips fail, drop the exercise on which you have plateaued for a period of time, swapping it with one or two that hit the same body part.