There are little, "rubber-bump", wear bar indicators located cross-ways to the tread that are down in the bottom of the tread pattern. They are spaced say every 6" to 8" around the circumference of the tire.
And if you can see/feel them and the tread is the same depth as they are, you really need to get new tires fast!!
Fwiw, I have bought several sets of tires from The Tire Rack, and located in centrasl Missouri, the UPS shipping charges are like $8 to $10/tire, plus about $10 or so for mounting and balancing locally.
I figure I save some on my tires b/c I can't get the selection locally that I get dealing with them! And save on the Taxes too! (Hassle factor, it's a wash)...
Open up "The Tire Rack" homepage and type in your tire size and hopefully you will find some tires that are discounted/on-sale that are4 the needed size and that have a high mileage wear rating along with a decent tread pattern that will suit your driving needs.
That's what I do.
And the other way to do this that I also have done is to just go to Walmarts or PepBoys, (or whoever you have locally), and look at their "Store" tire brands and see if they have a size that fits your car. (Walmarts is "Douglass")..
I just bought a set of (4), P/U truck tires yesterday from Walmart b/c they were actually cheaper then The Tire rack...
Tires are rated A, B and C and have a tread life number on them like from 280 to 620 or so. The higher this number, the supposed longer a tire will wear.
Cheaper, A and B rated tires with wear ratings above 400 are good value for the money, imho..
Sumitomo HTR Z and Yokohama Avid Touring are both GOOD, inexpensive, tire values for the money, imho... And I figure now several others that are newer brands too..
I have Sumitomo HTZ's on my car now..
Good luck with buying tires AND watch out for the B/S tire Sellers!!
And the only way you will be protected from them is by reading up on tires and learning about them!!
Hope this helps, but definately go out and see if you can see the wear indicators I described above!!