Too general for me to offer much other than:
1) don't give them scraps (People food), it can be done with care, but not if there is a weight concern
2) Grain free best if using kibble, I believe in general, many dogs don't seem to have a problem with popular (lower cost mostly) kibble A mix sith some, no more than half of feeding quantity of canned/wet dog food should help balance diet and give the dog something fun to eat. Treats? Sparingly and hard treats that help clean the teeth may be best.
3) I'd not take a dog to the vet for a checkup more than once a year...longer if there are no issues and I don't need to get shots for the dog, or a prescription renewal for worms.