Do you know if it is coming up from your lungs, or down from the back of your nose?
Drinking cows milk can cause increased mucus. Avoid cows milk.
If it is caused by an infection, the solution is to treat the infection. You could take oregano oil internally, and inhale eucaluptus oil (it must be 100%). Also expose your skin to sunlight, avoid sugar, and do everything which promotes immunity.
Try the above first, but if it is excessive mucus secretion without an infection, golden seal will be beneficial.
This is a really brief explanation. The idea would be to narrow it down to a specific cause, then treat it accordingly.