My first suggestion Kenneth, would be to not use the yellow letters. They are getting over used, therefore people just discard them since they assume you are trying to sell them something.
There are a few ways to find properties, and I will give a list of some of them:
1. Bandit Signs
Check with the building department in your county to find out what the laws are regarding putting them up. In my area, it is not legal in my county or city. What I do is put them out after 5pm on Friday(after city/county officials are done for the week), then go pick them back up Sunday night. This way your message gets out there for the entire weekend, and you don't get your signs taken down by code enforcement.
2. Car magnets
Kind of do a "We Buy Houses" car magnet. You're driving around anyway, so you might as well get some free advertising out of it. We are in the process of using car magnets to attract cash buyers in the same way.
3. Craigslist and other free sites
Post the "We Buy Houses" type of ads, and if you don't get any responses, at least it didn't cost you anything.
4. Bird Dogs
In case you don't know what Bird Dogs are, they are people you hire to find you vacant houses. You pay them $5 or $10 per house to bring you leads.
5. Driving for Dollars
This is essentially what you would pay Bird Dogs to do for you, only you are doing it yourself. You're looking for vacant houses. Look for really tall grass, a lockbox on the door but no realtor sign in the yard, mail piling up at the mailbox, piles of newspapers, no blinds or curtains, etc. Then you can either look up the owner through the county assessor's office in your area, or mail a postcard or letter to the address of the property you are interested in. If you mail to the address of the property you are interested in, and want to make sure the owner gets your mailing wherever they live, write "Address Service Requested." This way the post office will get it to the owner even if they don't live at the address of the property you're interested in. Alternatively, you can send out a mass mailing by area, neighborhood, or zip code in order to find all of the vacant houses within that specific area. You send out your mailers to the area you decide on, and write "Return Service Requested." Then, the post office will let you know which houses they know are vacant within the area that you mailed to.
6. Realtors
Realtors can be a very valuable asset as far as finding regular listings, REO's, etc. You just need to tell them what you are looking for, and they can usually set-up a search in the MLS system so that anything that falls within your requirements will automatically be emailed to you.
7. Pay for or Rent a List
There are services that will rent you a list or give you access to a list of motivated sellers for a one-time fee, or a monthly charge. I purchased a list from Kent Clothier of motivated Sellers. There are 1,000's of listings I get from him, and they are always updating the list. It cost about $1,000, but it saves me from looking for properties all day.
I hope this will get you started in the right direction. Good luck.