Some cheap and effective Do It Yourself Home Security tips.

Lock your locks!!  Even when leaving you should always lock your deadbolt and knob.  I know it's a painful time consuming task...NOT!!  For those of you who have two sided Deadbolts and can't be bothered locking it from the inside when you get home because it's to much of a pain to try to unlock it when you leave in the Morning with your arms laden with cups of coffee, purses, briefcases and etc....most knobs can be kicked/broken off, or doors kicked in or pried open when only the knob is locked...a deadbolt extends further into the door jam and will make this harder...especially if you install extra long screws on the latch plate that reach all the way back into the stud behind the door jam/frame!!

A good friend of mine recently opened her front door and had to fight off an attacker...if her Deadbolt on her Security door had been locked he would not have been able to force himself into the interior door when she answered it. Once she fought him off...he then broke the window next to the door in an attempt to gain entry...if he'd succeeded in breaking the second pane of glass he would've been able to simply reach in and unlock her interior door!! I cannot tell you how many times I have found windows unlocked or opened next to doors and simply reached in and unlocked them or found other windows unlocked or easily opened to climb through to get my customers into their homes. 
Have  a crack/space between the door and the frame big enough to slip a credit card or hacksaw blade or screw driver/butter knife, etc. in near the door knob latch...go to Home Depot or Lowe's etc. and buy a Latch Guard.  This will prevent someone from being able to pry open your knob, just in case you forget to lock your deadbolt!! But we won't forget to lock that Deadbolt from now on, will we? You may have to modify your door frame...chisel away a part of the frame for it to fit properly...but it's well worth the small cost and effort!! They usually cost less than $15.00 at Hardware Stores.
Do you have a sliding glass door? Do not depend on the lock in the handle to keep someone out. You would be amazed at how ineffective those locks truly are!  Get a which snaps into place and must be squeezed or pushed to lift it up when you open it, that way it cannot be pushed up out of the way with a coat hanger, etc like sticks can be!! They usually cost under $20.00 at Home Depot, Lowes, etc.  They also make little locks that attach to the Sliding Glass door that have a peg which goes into the frame when locked and cost around $6.00. I always recommend both and use both on my own home!! 
For your windows, get those little locks that go on the window tracks with a thumb screw and tighten them securely. You can usually find them at hardware stores for .99 cents to $1.99 each and will allow you to keep your windows partially opened  to enjoy the beautiful Spring air, while preventing someone from crawling through it while you are sleeping.
What? No peephole? Go to Home Depot or Lowes and GET ONE!!! If you have a security door with bars that would obstruct your vision through the peephole, install the peephole off to the side inbetween the bars. This is about safety not curb appeal. I also highly recommend replacing your exterior lights nearest your doors with Motion Sensors.  They are relatively cheap and easy to install in place of an existing light can often times find them so similar in shape and size to your existing fixture that you will not even have to do any painting to cover up where the old light was!! Costs on these vary but I got mine for $39.99 and it took less than 15 minutes to remove the old one and install the new one, and I'm a girl.
Granted, if someone wants in bad enough, they will no doubt get in...but these few little things may be enough to send a prospective burglar scurrying over to your neighbors where gaining access may be less troublesome!!
If you have a panic button on your car keys that will make your alarm go off, place your keys by your bed at night.  Most are powerful enough to set off your car alarm from anywhere inside your home. Never answer your door without your finger on that panic button! Hold in the hand that it out of view and push that button if you feel uncomfortable whatsoever!!  It's easy enough to turn off!  Trust your instincts...don't wait until you are in a panic situation...set that alarm off early, as soon as you have the slightest gnawing in your gut that something may be amiss. Always trust your instincts, neighbors are easy to apologize to, healing yourself and home is much harder.
For the Elderly, if you have a panic button on your car keys, carry them with you when in the house and when working in the yard. That panic button will come in handy if you fall, or etc.!!
If you purchase a home, ALWAYS get your locks rekeyed! There's no telling how many keys may be out there, even when it's a brand new home there are often several keys floating around amongst Realtors and Contractors. Some Home Warranty's actually cover or offer large discounts for rekeying. If renting, request your Landlord or Property Manager have the premises rekeyed once you  move in. Even if they claim the last tenant returned ALL the keys, they have no way of knowing how many keys the previous tenants teenage children gave out to their friends!!!
If your lock has developed a bad attitude, try lubricating it and checking the alignment with the latch plate.  Hinges will sag, and homes will settle, causing alignment problems.  Often times if you look closely at the Latch Plate you will be able to see tell tale signs that the locks latch is binding against it, grab a file and get to work, just a little at a time until all is working smoothly again.
Have any additional ideas or comments please let me know.... I will gladly add them!

Received a great suggestion from Thomas today....
"I have found that when the door is starting to drag at the bottom of the frame that a small piece of cardboard, like from a notebook paper pad , works great when placed behind the lower hinge of the levers just enough to pick the door off the frame can add 2 pieces if it is not enough...and sometimes 1 in the middle hinge, depending on the door weight."

In addition, though a much less common problem, you can do the same to the upper hinge if the door is scraping at the top of the frame. I sometimes use small washers or tabs off of soda cans, to accomplish this same thing and have found it works extremely well on Gates!  Thank you for your input Thomas!

Have an RV, Camper, Tent Trailer, Toy Hualer etc.? Do your keys say CH751? If so you might wanna replace those locks. It is estimated that over 70%  of all RV's use this same exact key for the storage compartments. This means the chances are very very high your neighbor has easy access to yours