Check your tire pressure every day, and top it off to maximum on the sidewall. Flat tires don't roll very easily.
When it comes time to replace tires, get a tire as slick as you can findg
Make sure your brakes are adjusted, so they don't rub (even a little) on the rims.
Make sure your seat is adjusted so that your leg is straight, if you are pedalling on your heels. That way, you get a little bend in your knee when you are pedalling with the balls of your feet. Makes for more efficient, and easier, pedalling. While you are at it, make sure it is adjusted (nose up or down) so that you don't slide fore or aft while riding.
If you have a shock mount on your seat or seatpost, get rid of it at the earliest convenience - they really rob energy.
If you have suspension on the front end, screw the preload as tight as you can, and if it has a lockout feature, use it, except on really rough surfaces.
Don't carry more weight than you need.......
Wear a helmet (ALWAYS) to protect your brain when you need it most.
Don't wear floppy clothes, if you can help it - you would be surprised ho much wind resistance it adds up to.
Try to get your cadence to a minimum of 60 RPM, and 80 will be much better. It is more efficient, and helps you go faster, farther, longer.
Concentrate on making circles with your pedals, not just mashing them on the down stroke.
Make horsepower (manpower) with pedal speed, rather than brute torque. Lots easier if your pedal cadence is 80 or so.
When it gets hard to pedal, you should have downshifted much earlier - think ahead.
Take advantage of the downhills for additional speed, and go uphill easier.
Stand and pedal when it gets too tough.
Drink water before you need it - it takes a long time to recover if you drink it to late.
The same goes for food ----- just monitor what kind you put in your pie hole - fruits and veggies are good, fats and sugars are bad....... LOL
In bicycling - it's all about the motor (YOU) ---- not the bike........ a strong motor, with good skills, goes faster, longer, farther.....
And MOST IMPORTANT - ride like everyone is trying to hit you -- and stay safe.... (Hi Vis stuff really does help - dark colors, and camo, is really for hunters)