Moving further into your property, the next "onion" layer is the buildings/outbuildings or stables.
Tidy up - try to ensure that all scrap metal is out of sight unless you intend to sell it - if you do, remember to use a reputable registered waste carrier and to check that any Company have the necessary certificates!
Store it away - any portable equipment should not be stored in isolated buildings that are not of a brick-built structure, concrete or heavy timber.
Fit good locks, secure windows - five-lever locking devices should be fitted to doors; if there are windows, then a suitable locking device should be used or if the window is not needed, block them up or fit steel bars, wood or metal shutters. If a padlock is needed, then a closed-shackled padlock should be used and consideration should be given to using a metal housing, welded to the door which will prevent bolt cutters or metal bars such as crowbars being used.
Good Lighting - lighting of buildings makes it more difficult for thieves to go "unseen". The cheapest form of lighting at this time is the "dusk to dawn" lights which do not require regulation and are relatively cheap to run.
Alternatively, if an area doesn't need permanent overnight lighting, the use of a photo-electric switch spotlight could be used in conjunction with a motion detector - this will illuminate any "night-time callers".
Extra security - invest in some ganders (male geese), yes, ganders. They are territorial, they can't be "bribed" with food and they are very noisy! They will alert you to anyone appearing whether expected or not....
Install cameras - it may also be prudent to install a simple CCTV monitoring system to work in conjunction with any lighting - some need no backlighting at all and can work in video, picture or audio mode; Bushnell, Pro-Stalk and Little Acorn brands warrant a particular mention for quality of picture, etc.