First of all....what media do you use?
second.....what temps are you germinating them at? (specify species too.)
thirdly.....how much ventillation and how much humidity?
and fourthly.....how much light, and what kind, sunlight or artificial?
On your first question, I use a 50:50 peat and silica sand mix for germinating nep seeds on. Makes it easier when transplanting them.
On the temps, I have them in household room temps, so like in the 70's or so.
On the Ventilation, I have all my seed pots covered with plastic bags for humidity. I mist them every other day.
On the lighting, I have my pots of seeds placed on south facing window sills receiving bright indirect natural sunlight. I seem to have pretty great results using this method so far.