What is cheapest way to check soil PH

Also when do you check it in relation to last time you watered. I know my water is about 6.9 maybe a little higher, but what can I use to check the soil that you can get at a local place that is very cheap. I don't plan on checking more than a few times. Thanks.

When working with soil the cheapest option for testing PH is very easy but not very accurate and I wouldn't advise it but i will give you the infor and then you can decide for yourself what you'd like to do.
When you have just watered and you get run-off (excess water) coming out the bottom of your pots, collect it. Test this water with a PH test strips.
Here is an example of the test strips http://cgi.ebay.co.uk/Tetra-Aquarium-PH-Test-Kit_W0QQitemZ270286186642QQcmdZViewItem?rvr_id=&rvr_id=&cguid=d51066a01260a0e202609330fee83572
You can use other PH testers which are far far better than the strips such as a truncheon eg:- http://cgi.ebay.co.uk/PH-TESTER-WAND-NUTRIENT-TRUNCHEON-METER-SET-EC-PPM-CF_W0QQitemZ260495689977QQcmdZViewItemQQptZUK_HomeGarden_Garden_PlantsSeedsBulbs_JN?hash=item3ca6c0c8f9

But if you can invest just a little bit of money the you can get a real soil PH tester which is best for testing soil, they come in very many types and you get what you pay for.
Heres a basic soil PH tester http://cgi.ebay.co.uk/SOIL-PH-LIGHT-MOISTURE-METER-garden-plant-greenhouse-UK_W0QQitemZ160404277048QQcmdZViewItemQQptZUK_Home_Garden_GardenEquipment_HandTools_SM?hash=item2558d70738

taste the dirt and see if it taste like batteries!!! J/K!!! go get sum test strips!!!

all of the above sounds about right,but also if your looking to get an idea,like just too high or too low,you can go to your local hydroponic garden center and get some disposable soil ph capsules,ther like $1 a test. depending on were u are,walmart may even have somthing simular,good luck