I also found that if I tried to think about it and not go with my gut feeling, then my success rate dropped to around 20% (chance). In other words, when I went with my intuition, I was right most of the time.
There's a risk of introducing bias here. When you get a low success rate, you might retroactively decide that you were in the wrong mental state and throw out the results. But if you got a high success rate, you'd assume the test was valid regardless of your mental state.
If you're consistently able to get in the right mental state and you never throw away results, then this isn't a problem. Otherwise you need to take another measurement. After you've received all the symbols but before you've checked your answers, decide on a scale of 1-10 how confident you are. Then you can see how well you did whenever your confidence was above a certain threshhold.
As I stated in the thread, I'm just beginning with this. I wanted to start with the PRELIMINARY TEST. The results have been very encouraging, but I don't work at a lab and don't know people that do. The goal of the thread is to come up with a scientific protocol for testing and then to find a group that will assist me with it.
That's fine, but it's maybe a little early to be talking about the preliminary test. The JREF isn't a psychic research foundation, so they're not going to want to put a lot of effort into helping you refine your abilities. They want you to refine your abilities and
then apply for the challenge. (And, remember, if you fail the preliminary, you have to wait a year before you re-apply.)
Likewise with local skeptics' groups. It'll be easier to set something up, but if you fail the first time it's not likely they'll ever give you a second chance.
Of course this thread's had a lot of good suggestions for tightening up the protocol, but probably the next step should be for you to get some friends to run you through a more formal version of the test. Once you're able to get consistent results, you can think about taking the preliminary test.
Also, the JREF will probably ask for three affidavits before they let you take the preliminary, so enlisting your friends will give you a head-start on the process.