Just for general oral hygiene?
Brush with an oral B oscillating head tooth brush. sonicare works fine but the oscillating movement basically sweeps in a more favorable direction along the gumline whereas the sonicare ones go side to side and sweep perpendicular to the gumline. small head is better, let the brush do the work just rest it on the tooth at the gumline at a 45 degree angle. the main goal of brushing is sweeping the plaque off at the junction of the tooth and gums.
floss at night, "hug" the tooth then you floss, use tom's of maine or some unwaxed floss to better remove plaque bc the slippery ones are easier yeah but don't work as well. something is better than nothing.
use fluoride toothpaste and an OTC fluoride rinse if you think you're at a higher risk
limit snacking, or if you must, rinse with water after at the very least. the constantly acidic environment is the real killer
waterpiks aren't bad but i mean i'm a dentist and wouldn't even waste my money on one.
go in for cleanings if your mouth isn't in the best shape to start with bc you won't be able to remove calculus at home
if you have dry mouth, use a dry mouth rinse before bed or there are these little lozenges you can stick on your gums that release xylitol and helps maintain salivary flow throughout the night
don't do any of the bs like oil pulling, charcoal toothpaste, whatever else is out there. at the very best it isn't doing any good.
oh yeah actually replace the toothbrush heads once in a while too. they wear down. no it isnt a gimmick to get you to spend more money.
there are other manual toothbrushes that work great for cleaning under the gumline. look up nimbus toothbrushes. or any kind that has extra fine projections extending beyond the thicker bristles. they're about 3mm long usually and you can see them sliding under your gums when you brush properly