As the weather warms grass, trees and shrubs will grow. With that growth comes the need for mowing and trimming. If you are not buying new equipment this year (or have not bought some already) then you need to perform beginning of season maintenance to the equipment you will be using. If you have someone else work on your equipment, you need to get your equipment on their schedule soon due to others having the same need.
If you maintain your own equipment, you probably should start with the largest piece until you have finished with the smallest piece. If you have a riding lawnmower, you need to check the battery. Most lawnmower batteries only last for three years at the most. The good news is that most lawnmower batteries are reasonably priced so if you need a replacement it will be easier on your wallet.
Next you should check the spark plug (or plugs). If the plug has build-up on it, or if it is cracked, consider replacing it. You should also check the gap on the plug to see if it is correct. If the plug is very oily, or light colored you may have either an engine problem, or carburetor adjustment issue. Since a spark plug is inexpensive, you should change it out unless it looks normal.
Another thing to check, clean and replace is the air filter. Sometimes a good cleaning will work, but in others (particularly if it has been operated around a lot of dust) it will be best to replace the filter. You should also change the oil and (and oil filter if equipped with one) making sure there are no leaks when you finish, and the oil level is full.
The next thing you should do is to remove and either sharpen your blades, or replace them. If the blades are dull, they will not cut well. Other things to check are worn tires, belts, fuel filter, linkage adjustments and grease fittings. These things may need care before starting the season.
Before putting the first drop of old gasoline in equipment consider using fresh gasoline instead. Even if the gasoline had a stabilizer in it, filling up with fresh gas is a good precaution. Looking at your other yard tools, make sure that air filters are cleaned and changed, spark plugs in good shape and cutting blades sharp. If there are any loose fittings, they should be tightened and grease used as needed. For things like rakes, hoes, manual clippers, etc., check all of them for tightness of bolts and screws. Additionally, make sure they are sharp.
Finally, if you do not have good safety equipment such as eye and ear protection, gloves, and boots you should invest in some. Once you have finished all of this work, you should be ready for a good part of the season barring any unforeseen issues.