Mending a Puncture
Punctures don't happen very often but when they do you'll want to be tooled up with this knowledge so read on.
It's a great idea to carry a spare inner tube because you can quickly swap the tubes and get on your way again. The punctured tube can then be repaired at your leisure.
Necessary tools: 1 or 2 tyre levers (plastic is better than metal), 1 x piece of sandpaper, 1 x tube of rubber glue, 1 x patch, 1 x pump OR 1 x piece of sandpaper, 1 x pump and 1 x glue less patch (if so skip steps 5 and 6).
1. If you don't have disc brakes you will need to release the calipers (the bits that hold the rubber pads) and remove the wheel. If you do have disc brakes you will only need to remove the wheel.
2. Use your tyre levers to remove one side of the tyre from the rim. This can be tricky but if you fully deflate the tube & push the tyre's sidewall away from the rim all along the side you will be removing first it should be easier. Then remove your inner tube.
3. Check the surface of the tyre for anything sharp stuck in it such as glass, thorns, nails etc. Then carefully run your fingers around the inside surface of the tyre checking for the same thing. If you find anything remove it. Also run your fingers around the inside of the rim feeling for anything sharp, there should be tape covering all spoke holes.
4. Find the hole in the tube by pumping it up and feeling/listening for escaping air or holding it under water and looking for bubbles. Mark the hole.
5. Use sandpaper to scuff the area around the puncture, this the glue make a strong bond.
6. Spread glue thinly and evenly over and around the hole and wait until it's dried to the point where it feels tacky to touch. Place a patch over the hole and apply pressure.
7. Put a little air in the tube so that it has shape. Place one edge of the tyre back onto the rim, leaving one off. Put the tube into the tyre/rim making sure to align the tube valve with its hole. Ensure the valve stem pointing straight up from the rim and that the tube isn't twisted. Now start to push the second edge of the tyre back onto the rim, starting at the point furthest from the tube valve and being careful not to catch the tube between the tyre and the rim. Most of this will go on easily but the final bit will be tough and you may need to use tyre levers to coax it over the rim - trying not to pinch the tube in the process. When complete, pump a little more air into the tube and check again that the tube isn't caught between the rim and the tyre.
8. Slide wheel back into place on the bike and tighten the quick release/nuts evenly - ensuring wheel is aligned correctly in the frame. Re-connect the brakes if you don't have disc brakes.
9. Pump up the tyre back to normal pressure and give the bike a quick ride to make sure the brakes are still working correctly.
Adjusting the Saddle
Your saddle should be high enough so that your leg almost (but not quite) fully extends at the bottom of each pedal stroke. If you want to be geeky the optimum bend in the knee is about 25 degrees.
You can raise or lower the saddle height by loosening the seat binder bolt or quick release and moving the seatpost up or down. Be careful not to raise the seatpost above the minimum insertion mark etched on the seatpost. If you go too high and find your legs straightening you will get lower back pain, if you go too low you will be making the biek much less efficient.
Adjusting the Brakes
Frequent cleaning is important for your brake pads and rims.
Regularly use a cloth and alcohol, glass paper, or even a file to remove dirt and grime. Brake pad surfaces should be soft enough that you can scratch them with your fingernail. To resurface worn or dirty pads, you can cut the surface with a sharp knife or rub them with sandpaper/file.
If your brake lever has a lot of travel, its likely that you need to adjust the cable tension.
The cable adjusters are usually on the brake lever (as well as the caliper with road bikes) and occasionally on the frame bosses (where the cable housing ends and the cable is then exposed, on the down tube). Wind the barrel adjuster, feeling the cable to make sure you are adding tension not removing it. Add tension until the brake lever feels solid and needs only a little movement to engage. Spin your wheel to see that it still spins freely and you haven't added too much tension.
Most brakes have a quick release to drop cable tension so the wheel can be removed so if your brakes are feeling very soft check this first.
Your local bike shop will be able to help you with any larger repairs and regular servicing of your bike.