I worm in April, late August and early November. Rotating through different wormers will keep birds from developing a resistance to a single ingredient, and not all wormers kill all worms.
Different ways to use each product:
SafeGuard (Panacur) 10%
1) 3cc per gallon of drinking water for 5 days. Some people use it for 3 days, others for 5 days. Repeat 10 days after initial treatment. This allows the worm eggs to hatch and the wormer will kill off the adults. (Wormers don't kill eggs.)
2) 1cc drench down throat for birds between 3 months and 1 year. Repeat after 10 days.
3) 1/2cc drench down throat for birds over 1 year
Valbazen (albendazole 11.36%)
0.40cc/lb, drench down throat
Ivomec for cattle
1) 3cc per gallon of drinking water for 24 hours
2) 1/2cc for birds over 6 months, given as subcutaneous injection or as drench down throat
3) 0.2cc for birds under 6 months, given as subcutaneous injection or drench
Treating via water is easier on the birds, so that's what many people do. As an example of what wormers kill which worms, read the labels. Ivermectin does not treat capillaria worms. There are other wormers available, but these seem to be the most commonly used. If you want others, I'll list a couple more.