when do i lock my bike: ANYTIME i'm not sitting on it. i've heard too many stories about "left it at home" or "just for a few seconds". if i'm not sitting on it, it's locked. done.

to the OP: i suggest staying away from on-guard products. for a little more money there's a HUGE increase in quality in the higher-end kryptonite and abus products, although they all make crap at the cheaper end of the scale. i also highly recommend the BikeRegistry Security Chain w/ Monobloc Padlock. it's very reasonably cheap and i was VERY impressed with the quality. it blew my on-guard "beast" chain out of the water. also, they're easy to deal with and their chains come with the stickers. before i saw them, i thought the stickers were a bit of a gimmick, but i'll order more when i get new bikes.

how you lock up your bike should account for:
a) where/when are you locking it up?
b) what kind of bike is it?
c) what other bikes are in the same area? or the same rack?
d) what's it worth to you (time, money, PITA, love, etc) to replace your bike?
e) what are your weight concerns?

there's no one-size-fits-all approach, but some things do work better.

http://www.streetfilms.org/hal-grade...-bike-locking/
http://www.streetfilms.org/hal-and-k...-bike-locking/
http://www.streetfilms.org/hal-grade...final-warning/
http://www.mechbgon.com/lock/index.html

sheldon brown's method of locking the rear wheel through the rear triangle is alright, but the biggest problem is that a lot of aspiring bike thieves will trash your bike trying to figure out how to get the frame out from around the lock. that's reason enough for me to not use that method.

here in wellington, it's rare that bikes get stolen when ANY lock is used. it's hard to even buy a good quality lock in this city! i've seen bikes locked up outside and unmolested for several months, using stuff from a hardware store that could be cut with a leatherman tool. i think i've only once seen a bike that was missing a wheel, and that took about a week. i can't outrun the bear, but i can outrun every other parked bike in this city!

i have heard stories about professional gangs that will fill a van with bikes in 2-3 minutes (from unattended parking garages while people are working upstairs) and then disappear into the sunset, but such stories are rare, and enough people use crap locks that 1-2 SOLID locks would be a deterrent, unless they just cut through the rack. even with the ideal tools, it would probably take more than 2-3 minutes just to cut through my primary lock, so those bad-guys probably can't afford to spend any time on it. whenever possible i put my lock around an electrical conduit, water lines, or something else that would discourage anyone from cutting through my anchor point.

there's an old rumor that 2-3 different types of tool are needed to cut U-locks, chains and cables. there is some truth in this, eg you can't cut a decent U-lock with a bolt-cutter, but there is such a thing as the "right tool" that will render any lock useless. there's no need for me to mention what tool it is, but anyone who steals bikes and drives a van already knows.

anyway, i grew up between NYC and philly, so even though wellington is a very safe place to park a bike, i'm somewhat paranoid and better safe than sorry. i'd rather carry some heavy locks than risk walking home (or worse, taking a bus ) and having to replace my bike. i can throw some very heavy locks in a pannier bag and i won't feel it.

i typically use a krypto-cable looped around the rack, through the front wheel, and attached to a NY-3000 going through the seat-stays, rear wheel and parking rack. there's no room in the U-lock for any leverage attacks, and it's unlikely that anyone will cut a 10mm krypto-cable to steal just a front tire.

i frequently park at a rack that doesn't work well with my bike and the NY-3000. when i'm going there i use a 7ft krypto-cable around the rack, through both wheels, attached to a NYFU holding the head-tube to the rack. still no room for leverage against the U-lock and still unlikely that anyone would cut the cable to get the wheels.

when i was cycling to work five days a week and parking for 8+ hours per day in an unattended basement parking garage (i worked upstairs) i left a heavy chain on the rack. i would use my NY-3000 through the rear wheel, chain-stays and rack, and the chain through the front wheel, front triangle and rack. i'd arrange it so that more than one section of rack would have to be cut out to remove both locks.

everything that easily unclips gets unclipped and comes with me. my saddle isn't expensive, but it doesn't look cheap and it would be hard to replace. from what i've heard, it's been years since anyone in wellington had a saddle stolen. i do have a "seat-saver" cable but i hardly ever use it. if i was in NYC or SFO i'd use the seat-saver, but here i think it would only make the saddle look more expensive/tempting than it really is. i often just tie a plastic shopping bag over the saddle: this protects it from rain, sunlight, pigeon poop, vomit, covetous eyes, etc. a little bit of duct-tape on the saddle would also discourage theft, but now we're getting into uglification, which is a whole 'nother topic

when you walk past any parked bikes, think to yourself: if i wanted to steal a bike, which bike would i steal? how would i steal it? what tools would i need? how long would it take? ONLY by thinking like a bike thief can you intuitively understand the best way to lock a bike under different circumstances.