Insurance - otherwise I have NFI.

Chemset a hardened eyelet into the floor, then chain and lock. Make it thick enough that you'll either need 4 foot bolt cutters or a angle grinder.
Cheers

i got a floor anchor from frasers and i have a

try something from here
http://lockitt.com/lockdown.htm
If it was mine I would go with loxins for the fixings so when you want to remove it there will be no bolt left exposed

but the best way by far is when building your home or shed is to have an anchor cast into the slab, not many people get that opportunity but those that do often don't think about it.

you can lay some pvc tube prior to concrete, just lower than the floor level, as the cement is starting to cure, push a front or rear tire into it, install a push button to a siren, (have an off switch behind a panel)
if your bike is moved, you will know, the thief will have no idea it is there or find it in the panic.
probably find a thief will try move the bike before finding a chain

Insurance is the best.
If your garage is anything like mine they would have access to angle grinders, 1mm disc's, Electric jack hammer, reciprocating saw etc etc anyway.
The house is alarmed with sensors in garage and I must say I like the sensor in the floor idea, would not be as visible as the current detectors I use.
I also have a big mother of a hardened chain and lock but never use it.
Ride Safe
Nigel

Agree that insurance is the best thing for peace of mind. My "floor anchor" weighs 44kg and he is my avatar!

I leave my garage unlocked and key in the ignition and still no fucker will take it...

Some very good answers here, but as stated most of use have the tools for them to use to cut the chain or cable anyway thats why i dont bother. I have 2 camera on my bike, and my entire property covered and an alarm. So anybody coming in will be caught on atleast 4 cameras, i have put extra locks on the rolla doors and i'm happy with that. If they are game enough to go that far i might as well help them load it up.

T1

 If a pro wantsit, hell get it, but for the rest, the longer a theif has to stay there to cut chain ect ect, the more chance hell be disturbed, And in a suburban area, an angle grinder is a lot of noise. An alarm that wakes the neibours in the middle of the night is enough to scare off the majority of the younger drug fucks.

I am a little surprised no one talks of disc locks and pad lock through the pulley/belt.
if you cant wheel it makes it difficult to take it.
Have heard stories of guys just putting a pipe or the like through the front wheel and hauling it away when a disc lock is fitted. Need 3 guys to do that and not sure if they would bother. Padlock the pulley/belt and you would need at least 4 guys.
Wonder how many bikes get taken from homes as opposed to the streets.

 if smeone wants to steel something they will get it if they want it bad enough, we can only try to slow down and deter the prosses fucking scum

www.kryptonitelock.com/Pages/HowToSecurePower.aspx

Just be aware the Garage ceiling needs to be quite high to accommodate one of these anchors, they work extremely well and are difficult to remove.

The Kryptonite Floor Anchor is easy to install and works well , re-inforced dynabolts and hardenned , can`t remember how much , $140 or something from MCA`s , the Kryptonite Hex Chains and Disc Locks are good gear as well !

@ Soapbox, see it's working already, thats my decoy anchor, the real one and luxury yacht I have, are hidden in the other Garden Shed.