The best way to avoid the comedown is to lower your overall dosage (keep it to 100-200mg). Further measures you can take (other than 5-HTP which is a good idea) are anti-oxidants, exercise & healthy food. Smart drugs, such as Piracetam, could also be a good idea.
I'm a big advocate that by keeping your overall consumption to below 100-200mg, you can avoid a negative comedown. Or at least reduce it significantly.