The best you can do really is and this method works for me fine and never had no problems at all.
Make sure you buy a good quality lock gold rating "new york"
https://www.amazon.co.uk/d/Cycling-Locks/Kryptonite-York-Standard-FlexFrame-Bracket/B005YPK9SY/ref=sr_1_1?ie=UTF8&qid=1489984658&sr=8-1&keywords=new+york+lock
when using the lock make sure you go around the frame and the wheel and use two locks one for each wheel and if you wanted to go a bit further put one around the frame too.
Then i would advise you haven some pin head for your wheels and your seat post if a bicycle is unable to be stolen the thief would steal parts of it
to make up another bike.
https://pinheadlocks.com/store/en/6-products
This should stop your wheels and saddle from being stolen off your bike
with 2 good quality locks around it you won't have to worry about your bike but i wouldn't be away from it to long
The reason why i would suggest pin heads because if they do steal your seat from your bike you are going to have a very hard and horrible ride home on your bike a quick release seat is so easy to steal seconds to get off and very frustrated for the cyclist
if you wanted to make sure that no one would want your bike at all then i would advise taken a Allen key with you to quickly take your pedals off is someone sees your bike with no pedals there is a higher chance of them moving on to the next bike to be stolen then even bothering with yours.
When a thief is looking to steal a bike they are looking for a quick get away and they don't want to be messing with locks at all they just want to get on it and ride it with no problems
They don't want to be messing with nuts and bolts because that is to much time to be bothering with they just want to cut the lock and go
job done
i think taken the pedals off is the best method because no thief is going to have a set of pedals with them to hand and they are not going to want to push your bike away they want to get on and ride it to where they need to be going
walking away with your bike is not a quick get away getting on and pedal quickly is a fast get away