Seat (Saddle) Adjustments
A mountain-bike seat will move in three directions: up and down, forward and back, and flat or angled up or down on the post. The proper seat height for most comfort and most efficient riding tends to be way higher than you've always been used to. This is a fact!
And if you find that climbing hills is often excessively painful, your seat probably is too low. It's now common knowledge that when your leg is at the bottom of a pedal stroke, it should be just shy of being completely extended. You'll need just a slight bend in the knee.
You may feel like you're too high on the seat, but in reality you'll only be sitting for about half of your riding time anyway. The other half of the time, you'll be standing on your pedals to get a better view of things to come.
Your riding will also be more efficient and safer if you can keep the front end of your bike lighter, especially on the downhill sections of your rides. In order to achieve this, move your weight further back on the bike by sliding the seat back on the post.
This is where the length of your upper body becomes more critical. If it seems that your arms are bent too much while grasping the bars and if it feels like your upper body is too close or hanging over the front of the bike, then you must slide the seat back, and in many cases way back, on the post.
A small adjustment in our seat forward or back on the post will often make a large transfer in weight distribution. Over time I have found on numerous occasions that beginner's seats usually need to be slid back.
Also, a steeper upward angle on the stem/headset (the top of the steering fork and the angled part that the handlebar attaches to) will also put you in a more upright position.
The standard straight and flat mountain bike handlebar system is now slowly being replaced with the riser bar. Riser handlebars put you in a more comfortable and upright position—which helps to prevent excessive bending strain on our necks and backs—and at the same time shifts your weight distribution slightly further to the rear.
Conversely, it should be noted that if you tend to have a short upper body and it seems like you're having trouble reaching the brakes, shifters, or bars, your seat may need to be moved forward a bit.
Lastly, the slope or tilt angle of your seat will also effect comfort and performance. Most riders will be comfortable with the seat angle flat (parallel) with the top tube between your legs, or slightly angled down toward the front of bike. This also makes it easier for you to slide forward or back off the seat—for downhills—more quickly and smoothly.
Pedals and Footwear
There are three main varieties of pedals: just plain platforms, clipless pedals, and toe clips or single-strap pedals.
Mountain biking safely requires that you do use a system that will help keep your foot on the pedal under all riding conditions. Each one of these pedal systems is entirely appropriate to use for riding. However, your past riding experience and how much you plan to ride will be helpful in determining the correct pedal system to start with.
For the vast majority of novices, I recommend the toe-clips-and-strap pedals, but if you're coming from a long history as a road rider and have become quite accustomed to clipless pedals, then it's entirely possible that you could start with clipless pedals.
In addition, if you grew up riding BMX and are still in good physical condition, then for you it's possible to use the special extra-wide platform system and the appropriate shoe that works best with it.
For all those other folks that may not have a BMX or roadie history, the following suggestions for starting with the toe-clip-and-strap system will be helpful.
Toe clips (the plastic basket part on the front of the pedal) come in different sizes. Some are very short for small foot sizes, others seem to fit the average foot size, while still others are extra long (or deep) for the big foot.
Your toe clip fits properly if, when you slide your foot into it, you're able to have almost the entire ball of your foot sitting on the pedal and not much space left empty at the end of the clip.
Remember, you can always get shorter or longer clips to accommodate your foot size; they're inexpensive. Straps that go around the clip come in a variety of fabrics. The best straps are made of very stiff fabric that will form and hold an open round shape, making it easier for your foot to enter and exit.
If you're unable to get the stiff material straps, you can spray them with a fabric-stiffening agent or the nontoxic variety of polyurethane.
How tight you make your strap will be up to you, but keep in mind that if they're too loose you'll lose the mechanical advantage of always having the pedal against the ball of your foot. Too tight, and it will be too difficult to slide in and out of them.
The best footwear to use with clip-and-strap pedals is a flat bottom (no or very little tread) sneaker. Any leather, high- or low-top, canvas or high-tech fabric sneaker will do fine.
The key to the footwear is be sure that it has no or very little tread. You want your foot to be able to slide in and out on the pedal easily, and a treaded shoe will not permit this smooth action.
If you're starting with clipless pedals and footwear and you have been a road rider, you'll quickly discover that there are very few smooth surfaces on dirt, so be prepared for lots of trial-and-error and falls.
One thing that may help make the transition easier is to adjust your shoe release mechanisms to the loosest settings. This will help you get your feet out quicker. As your body adjusts to the difference in terrain you'll become more confident and be able to tighten up your settings later as your balance improves.
Also, if or when you decide to go over to clipless from the clip-and-strap system, start by riding on wide fire roads or pavement and keep clipping in and out.
Practice makes perfect.