I have been giving an adult (15lb!) cat and two kittens oral meds for the last month, so I'll tell you how I do it (and how my vet showed me to do it).
1. get the meds ready (in syring, or whatever on the floor) and have a very tasty treat ready too.
2. get the cat and sit down indian-style on the floor beside the meds(legs crossed).
3. Face the cat away from you and put the cat's hindquarters between your legs and hold them with your legs.
4. scruff cat with left hand, pull head back while scruffing, and inject stuff with right hand. OR, use left hand below chin and press gums into teetch (so that he has to open his mouth and can't bite you without biting him gums) and inject meds once mouth is open.
5. Release kitty immediately (if not struggling) and give him said tastey treat and praise.
I would suggust putting the syringe as far back in his mouth as possible before squirting and make it as fast as possible (less chance of wriggling).
Also, if your cat is prone to spitting up the meds, as one of my kittens was, hold his head with his chin pointed up and stroke his throat to initiate swallowing and keep his head tilted up for a while. It also helps not to feed right after if he is prone to throwing up the meds.
I always try to give a treat or an entire meal soon after meds so that the cats knew that they mgiht have to get meds, but they would be rewarded after.
p.s. if you are really having a hard time (with head thrashing, trying to bite, etc, I highly reccomend welder's long gloves...this saved me when I was first giving my 15lb (notoriously hard to give meds to) cat. He could try to close his mouth, but I was not worried because I had thick rawhide gloves on.