To wash the column (no regeneration really takes place, just cleaning), here are a few comments:
Contact the column manufacturer for informed suggestions. They usually include a document with each new column which provides suggestions on the care, use and washing of the column.
Most wash solvents simply utilize a stronger mobile phase than what you used in your methods. The goal is to remove any fouling, build-up or strongly retained material which was not eluted off the column. For example: Start by making sure no buffers or salts are inside the column. Use an aqueous or organic mixtures which is free of all salts, additives and buffers and flush the column down. Pure or high concentrations of ACN are usually strong enough to elute most compounds. MeOH too, with water, is useful in this regard. Avoid the use of any detergents as these can be very difficult to remove. Again, the column manufacturer should be able to suggest a mobile phase mix that is most applicable to their column phase and your described use.
In some case, reversing the column (backflushing) is beneficial. I would strongly recommend trying the above suggestions first though.