I just got a new bike and I want to make sure I’m able to keep it up properly. I am entirely new to this.
Edit: thank you all for your responses, I’ll keep these all in mind and I’m adding them to my reminders to make sure I remember.
Know what pressure your tires should be at (range is written on the sidewalls). Check and re-inflate tires to proper pressure every ride, or every couple of days if you are riding regularly. You'll soon find out how often tires need some air.
Check and adjust brakes.
Clean chain, sprockets, idlers, chainrings; re-lubricate the chain. How often depends on how much you are riding and in what conditions.
Generally keep the bike clean.
Adjust derailleur indexing as needed. Check chain wear.
Periodically, check for rattles, and anything loose. Once a bike starts to get some miles on it you can check headset, bottom bracket, wheel bearings for play. Make sure pedals are tight in the cranks. Check wheel rims are true.
Eventually you start wearing things out: brake pads, tires and chain are the primary wear items. If shifting accuracy is suffering changing out cables and housings is necessary. Brake cables and housings can also be replaced.
There are plenty of guidance videos on YouTube to help you with specifics of all of the above. Personally I like the Global Cycling Network Tech and Park Tool's YouTube channels (and articles on their web site). I'd definitely recommend learning how to clean you bike properly as it has a substantial effect on how it performs.
Start by pumping up your tyres. If they don't inflate, then fix that first. With the tyres inflated, go over every bolt holding the bike together and check that nothing is loose. Next, check your brakes by spinning the wheel to see if they rub when not engaged (could need brake adjust or wheel true). When the wheel is spinning, pull the brake levers. You should be able to apply sufficient braking without pulling the lever through to the bar.
After that, you'll want to focus on the drivetrain. Start with the shifting at the rear. Ensure that the limit screws are correcty adjusted to allow shifting onto the smallest and biggest cogs without going any further (particularly not into the spokes). Check that the cable tension allows you to shift smoothly through the whole range. Repeat this process on the front, then move onto the chain. When spinning the pedals backwards, there should not be any stiff links causing more resistance or a bit of a jump forward. The chain should also not be squeaking if well lubricated. Using a chain checker tool (most bike shops will check this for free) see how worn the chain is. If the chain is worn, then it needs to be replaced. If it is very worn, then the cassette/cogs and even perhaps the chainrings might need replacing.
Once the drivetrain is running well, you'll want to check that the headset is tight enough and that the bearings there and in the bottom bracket are still smooth. This should cover just about everything but even eith all of this done, it can be a good idea to lift the bike 30 cm off the ground amd drop it to listen for any rattles that you would not hear in a well maintained bike.