Unless you do your fecal floats periodically to determine your worm load (and you'd be looking for round worms, cecal, capillaria, tape), it is generally a good idea to worm seasonally as by the time you see evidence, you've already got a severe load. The goal of worming is to keep the worm load down. It is very unlikely you'll ever eradicate it. Most chickens (dare I say all?) have worms whether they show symptoms or not. Many choose to worm in fall and spring.
It is best to rotate wormers so that the worms don't build up a resistance and of course keep clean litter and use field rotation to reduce the worm load in the environment. If you are concerned about egg pulling, or selling eggs, currently the only FDA layer approved wormer is Hygromycin B which is the Rooster Booster Triple Action Multi Wormer or Durvet's Strike III. Both are a pelleted feed additive. The advantage of Hygromycin B is that there is no egg pulling, and it targets the 3 main worms (round, capillaria, cecal). The negative is you cannot monitor each individual bird's dosage to make sure the greedy one's don't gobble more up while the less dominant ones don't get the recommended dosage. (You simply add it to the feed by ratio and mix).
The advantage of other wormers is you can add it to the water or put the paste in a treat (like a raspberry) so the birds generally get a fairly even dose, however, those meds are off label. If you sell eggs, that is problematic. If you don't, then just use the rule of thumb 10 to 14 days pull time for eggs, although Ivermectin has shown to clear the system within 7 days and is effective against internal and external worms IF you apply in the water (I believe cattle injectable is used for that) and re-dose in 3 consecutive dosages 7 days apart. For external parasites, I use the cattle pour Ivermectin and apply a small drop at the base of the neck and vent, again 3 consecutive times, 7 days apart.
Unless you know you are in an area that has had problems with gape worm, I wouldn't worry about it. Gapeworms are rare in most backyard flocks. Fenbendazole (Safeguard) works against gapeworm if you are concerned.
There is research to support pumpkin seeds and cayenne pepper as worm expellents, however they only expel live worms not dead ones. Field rotation is essential if you choose to use herbal methods. I started with herbal, but after time had to resort to meds as the herbal only helps retard the growth but does nothing to break the cycle.
As a Vet Tech, you will have ample knowledge to look up meds and monitor your chickens health. My daughter became a Vet Tech, and we used my flock for a number of studies and treatments. That knowledge really helps.
Most of chicken care is keeping them clean and well fed/watered.
Edited by Lady of McCamley - 1/8/16 at 9:12pm