Do keep in mind this does not make a complete list of things new riders should know, but at the very beginning of your motorcycling journey, it would do new motorcyclists well to remember these, among others, whether you plan to ride a motorcycle on a daily basis or only for leisurely weekend rides.
Brakes are the most powerful part of any motorcycle. Think about it, how long does it take the engine to bring you up to 100km/hr (62 miles/hr) and over what distance? Now how long do the brakes take to bring that down to a big fat zero and what is the braking distance covered? Now that you kinda understand that, lets look at the braking assembly? The most common braking systems on motorcycles are hydraulic discs, followed by drum brakes.
In hydraulic systems, you have the master cylinder, brake pump assembly, brake lines, caliper and brake pads. Seals on brake pump assemblies can leak but it is a gradual one, thank goodness. You will find braking soft and squishy and also see excessive oil at the plunger where the brake lever contacts the pump and those are your giveaway signs.
Air and water ingress also leads to squishier ineffective braking. Somehow the characteristics of brake fluid that make it resistant to heat also attracts water. This water boils under pressure and temperature during heavy braking conditions, causing vapour build up that also adds to soft and squishy brakes. Vapour is compressible, oil and water are not. Hence softer and more excessive pull on the brake lever than normal is also a sign that you are not getting as effective braking as you should. Brake lines can be bled whenever this happens or during pump kit replacement. Just to play it safe, if you have not experienced such issues you may also bleed brakes once a year to replace the old brake fluid for new.
Brake pads also wear out, but how fast depends on your usage. I had to replace mine almost monthly on my dirtbike, with an average of 4 leisurely off road sessions a month. More hardcore off-roaders will replace brake pads with higher frequency. Road only machines will not be as high but you will still need to check ever so often. Uneven wear on brake pads, such as more on one end vs the other resulting in a slanted look can indicate a seized up caliper piston(s). If you have no experience on DIY, you can always ask your friendly mechanic to do it for you.
And while you check your brakes, you might as well check all your lights too. Busted brake lights at night are seriously only going to put you in danger.