Soil test kits

Bought one when they were on offer in Aldi, the type that you push in the ground and read the meter, must say it was pretty accurate, I also used the test kit using soil sample and water at the same time, it read much the same as the electronic one.
After doing a few spot tests around the plot I found that my soild was slightly acidic, so I limed it year before last.  

I have tried the stick in the soil probes and the results are not very consistent. Chemical kits as Momofstig advises work well.

Rather than taking spot samples you should aim to get an average pH for each section of your plot. i.e. last years brassica area, potato area etc. as you will be liming section by section and not spot by spot.

To achieve this take a bucket and a trowell and take several trowell size samples  to a depth of about 6 inches from a section. Mix them together well in the bucket and then test samples of that.

With spot samples you can hit a place where lime or fertilizer has been spilt, there is a lump of compost, a cat or other creature has peed and other variables which may give strange results.

I've found that the only accurate way to measure soil is with the chemical kits. I bought one of those push in things and it was useless as it gave such wildly varying results...anything from pH5 to pH9. With that kind of variation you have no idea what to do with your soil.

Whereas my push in model was equally unhelpful showing pH of 7.00 everywhere, even in the ericaceous compost bought that morning 

Now have a chemical testing kit, which shows the soil to be much more alkaline over most of the plot