What causes valve train tick in 1998 Caravan 3.0 liter and what's the fix Seems worst at startup?

More than likely varnish or trash buildup inside a lifter. I have used this product (Seafoam Motor Treatment) many times and it can work wonders. You can purchase at many auto parts stores, such as Advance, Pep-Boys, etc. You may have to ask for it. Follow the directions explicitly. This is not one of the snake oil products and does work as advertised. Read about it here. http://www.seafoamsales.com/motorTuneUpConsumer.htm