My bikeposts were well received and I plan to do more, but I'd like to reach out as to whether there's a topic or maybe specific questions about the whole ordeal that interests the users of this site specifically?
Like do you want to learn about tools you need for more than basic maintenance? Tips on riding in winter conditions and/or in the street with car traffic? Maybe which of the marketing buzzwords are actually important? How to train for longer rides? How to bike commute / when to bike commute?
Hit me up, I'll try to answer any question and/or do another bikepost about any topics that you're interested in and I feel qualified to answer.
I'm assuming this means the actual locking mechanism, i.e. where you put the keys in. A cover for the keyhole helps, allthough if that's not built in, it'll be a nuisance to retrofit. Carry a bic lighter (either on the bike or in your pocket) for this.
If you have a derailleur and a slack chain, it means the chain is too long and you need to shorten it. If it used to be tight and now isn't with no other changes, replace your chain.
If it's something with rear dropouts, flip your bike, loosen the quick-release screw or the bolts that keep the wheel in place and pull it back a bit. If you're already at the end of the droput, it's either time to shorten your chain or, more likely, to replace it as it has worn out. Chains do actually stretch, very slow,y over time.
EDIT: Do note, if the chain used to be of proper length and now isn't either with a derailleur or because you're at the end of the drop outs, there's a high chance your front and rear cassete (the different sized cogs) are now worn down to a point where they fit with your old chain only and any new chain will slip constantly. Either replace them yourselves, allthough that's not so easy, or keep your old chain and book an appointment with a shop soon to do it all in one go.
For it to not go out of balance from the frame, tighten whatever holds it in place more, but do it so it is actually in balance. This usually means you want to use both sides of whatever is holding it there either at the same time (like with a quick-release skewer) or you want to alternate the tightening with half or quarter tuns when you get to a point you can't tighten by hand anymore.
You can use Zipties or velcro-zipties attached to the chainstays to check how centered it is. Put it in, give it a whirl and if the distance changes between the ziptie and the wheel, you need to adjust.
If the wheel tightly secured in the frame and it still gets out of balance, there's a mixture of things to do. You might need to get it trued, which unless you're really into it, you probably want a shop to do. Alternatively, get a new rear wheel. They do eventually go bad.
To prevent this from happening, try and put less stress on it. There's guides out there how to ride over curbs or edges (I'm assuming you're not mountain biking down trails). It usually involves pulling the front wheel up while standing, then shifting your weight forward a bit so the rear wheel takes less of a hit. Next step would be bunnyhopping the bike, allthough that's pretty much an advanced level skill unless you're clipped in to the pedals.
Wow, I didn't know the chains themselves could stretch out, thanks for the advice!
It's pretty much inperceivable to human eyes, but it does happen and seeing as the gap on the chain needs to fit in the tooth of the cogs, you do eventually run into problems if those don't match up very well.
For chain locks (the kind with a metal chain with a nylon sheath and a separate lock), just keep the lock away from moisture at all costs to avoid freezing. The delivery-guy method of wrapping the lock in a plastic bag is surprisingly effective. If it does freeze, percussive maintenance usually does the trick to get it unstuck.