Bike servicing / maintenance

Check your bike(s) if they use integrated headsets.

If they do, they are by far the easiest bearings to maintain on a bike. All you need to do is to dismantle the stem and top cap from the fork steerer, then drop the fork out. Once the steerer is out of the head tube, you can pull the headset bearings out with your fingers.

Clean them, then check for grittiness or resistance. If there is, you'll have to replace them soon. If not, regrease and reinstall.

Apart from taking out the seatpost every 6 months or so for a wipe and a fresh smear of grease, just keep the chain clean and lubed (sparingly!) and occasionally stick a chain wear checker in it.

Then just fix / replace stuff as it breaks / wears out / stops working.  Buy tools as and when required.

The interweb is a great source of advice on how to do stuff.  YouTube is especially handy; you get to watch somebody actually doing the thing you're interested in.

From quite a timid start I've gradually built up tools and confidence and now do everything myself.  A pushbike isn't a complicated machine at all.

Couple of years ago I bought a carbon frameset because a bike shop in the northeast was knocking them out for £500 and I'd always wanted a CR1.   I stripped all the components off my alu bike and built up the carbon one.  99% of it fitted the new frame; only the seatpost was a different size. 

Then I gradually accumulated enough extra bits to build 2 complete bikes, so most of it came off again.  All the better / lighter stuff is now on the CR1 and the tattier / heavier on the now dedicated wet weather alu bike.  Great learning experience and a way of achieving N+1 gradually.

I find friction on cables mainly results in them not releasing as smoothly as they should, e.g. Brakes work fine but maybe don't open out again evenly and might cause pads to rub. Gears would change onto a bigger cog fine but stick when going smaller. On my commuter I've got old style downtube shifters, and I have to overshoot the indexing point(the 'notch' for the gear) then go back when changing into a faster gear (but if I loosen the cable it ruins the positions) , which is a sure sign I should be changing my cables instead of playing on the internet!

If you want to improve your confidence in the more advanced/scary skills, some councils offer heavily discounted maintenance courses (I think mine was about a tenner for a fairly advanced course thanks to Lewisham council) and lots of bike shops run them too. It's great to know you can fix anything on your bike yourself! 

Buy a maintenance stand. Makes everything so much easier. Well actually makes maintenance easier wont help with everything.

Servicing cycles is easy, watch a bunch of videos, get a set of tools, some are particular to each manufacturer, Shimano, Campagnolo etc. They are not expensive and don't buy over priced pro versions for home servicing. You will be using these twice a year and will last years if treated properly. Get a pot of copper grease, decent lithium grease and a spray oil. Also a tin of brake cleaner for de-greasing parts. Modern bikes have many Allen heads and specific torque settings on certain bolts, get a good torque wrench 5-50nm. This will do for all bolt settings on a bike

It's hard to say... Lubrication advice above is absolutely correct, but when it comes to tools, there are innumerable variables.

Absolute minimum would be some decent Allen keys, a couple of screwdrivers, and maybe... But only maybe... a chaintool. Investing in a torque wrench is always worthwhile.

Beyond that, you're into the realms of changing cassettes, cables and chainrings all of which need specialist tools. A basic 30-50 piece toolkit will cover all of these. Not a lot of money or a big space commitment for a passable on of them eg http://www.planetx.co.uk/i/q/TOJW30PCTK/jobsworth-pro-workshop-quality-3...

Once you move into bearings then you're talking a whole batch of special tools and unless you have a fleet of bikes is usually more sensible to pay someone else to do.

Keep the bike clean, chain lubed and depending on your mileage...get a proper service done by a recommended Bike Mechanic or LBS.... at a 6 month or annual basis...if you Sportive/Race then most decent Bike Mechanics will sort a bespoke service/maintenance plan for you... 

Easy self maintenance; chain, rear cassette, brake pads, cables.

Replace chains early, and you should go through 2-3 for each cassette. Brake pads are trivial. Cables will fray over time introducing extra friction, replacing just the inners is usually fine and saves the hassle of wrapping the handlebars (but learn to do that anyway, because new tape is nice).

More complicated maintenance involves the bearings. That's a matter of grease and/or replacing parts. Leave that to a bike shop unless you're confident and happy to learn and buy a few tools.

Two other things your bike shop will do that everyone should be doing themselves.  Take the seatpost out and push a rag down the seat tube.  Turn the bike upside down and clean the cable guides under the bottom bracket. 

Frequency of course depends on mileage. I always do my own annual service about this time of year, after riding through the winter.

Lube anything that moves. Namely, derailleur and brake pivot points. Check bearings (bottom bracket, headset, wheels) for grittiness and adjust/regrease/replace as necessary. Every now and then, make sure that your seatpost moves in the frame. Keep an eye on gear and brake cables, cleaning and lubing when friction builds up. RD jockey wheels will get lots of crud in them - clean and lube regularly.

I think that's about it. Don't do what my mate does, which is drench the  entire bike in degreaser and marvel at how shiny it is.