Hi, l bought a cheap second hand bike a few weeks ago & am fairly clueless with it. l only ride it to work (around 10 minutes) a couple of times a week, but am pretty worried about the brakes. They squeak unbearably loudly whenever l put even the slightest bit of pressure on them, and when l do really have to use them they do not seem to be as responsive as they should be. Does anyone have any advice to stop the squeaking & make the brakes a little safer?
And would not oil make them much more dangerous?!

put a little bit of oil on them

if you chain is the problem why you bike is squeaky you can put some wd-40 its a oil spary its helps your chain less squeaky but you can only put it on certain places.

need any more help add me and l will tell you

You can try this tutorial and see if you can get them to work better.
Be sure to clean the braking surfaces of the rim.

http://bicycletutor.com/part/brake/

If sanding the pads do not help they may be too old and hard, pick up some new pads at the local bike shop.

first of all never put oil on ur brakes because that will mess up the braking surface.
you should toe in ur brakes which means ur front brake pads should be hitting the rims before ur back does this eliminates the squeaky sound. if u do not know how to do this u can give the bike to ur local bike shop & have them do it for 5 bucks. l will also recommend looking at a company called kool-stop they have very good brake pads that do not squeak & work excellent in harsh weather.

sand your brake pads. or just get new ones

It’s just a squeaking because its rubber on metal & if the brakes r not slowing u down enough that’s just because the r too far away from the rim. All u have to do is 4 simple things:
1)Hold the brake callipers so they r both at least 2-3mm away from the rim
2)Undo the bolt holding the brake cable
3)Pull the cable tight & do up the bolt as hard as u can so it won’t come loose
4)Test the bike & ensure the brakes r ok
If u have any further trouble just email me at (brett.cass.com)