Suspension depends on spring rate, valve shim stacks, and clicker adjustments. First, If you want to have good suspension you have to install springs that are the correct rate for your size. Depending on your weight and riding style you might need to get some aftermarket springs.
After you have purchased your springs you may want to re-valve your front forks for better characteristics for the new spring rates. For older or worn out dirt bikes, Race-Tech Gold Valves work great because they give the feeling of newer and more modern suspension. If you own a newer or mid 90s KX 2-stroke I suggest installing washers below the springs to lower the rear end and offer better cornering on tight tracks. For bikes such as the Yamaha or Honda I would suggest an aftermarket rear linkage to help them in straight-away stability and jumping.
Oil weight can also affect dampening, or the rate at which the suspension bottoms out. A 5-weight oil is usually used on trail riding applications, for MX style jumps a 7.5 weight oil (if available) would be better preferred. for large MX jumps, arenacross tracks, and supercross tracks 10 to 15 weight oil should be used. By using the correct oil weight you can avoid spending $200 on Gold-Valves and Shims although they are highly recommended. Next, set your rear sag on your shock.
Once you have set your sag you can now play around with your dampening and clicker adjustments to create a soft and plush feeling or a racy type firm feeling that offers more comfort when jumping larger jumps and cornering at higher speeds than what your stock settings are intended for. You can’t forget that stock settings performed by the manufacturer’s are for the average adult rider, not an A-class or B-class racer. If you need any help post a comment regarding your question for suspension.