I'm not sure that's really a good way. So a judge rulled one way 5 years ago. So what? He could rule however he wanted next year. You may think you have an idea... but maybe he had a death in the family and it changed his outlook on life. Maybe he gets a drinking problem. Maybe his wife scolds him everyday. Who knows.
Actually, the best way to know how a person will vote 10 years from now is to actually know the person for a long time. Not just read about them.
That's why you look at a long term track record. If a guy has been basing his rulings on an originalist judicial philosophy for 10 years, then the odds are pretty high that he will continue to do so.
I think you are still stuck on individual rulings like "did she rule against gun control" or something like that. It doesn't matter if the result of the case seemed to be for or against conservatism, it only matters how the person came to the decision.
This is why republicans are baffled when a guy that ruled against abortion 5 years ago and then makes a ruling seemingly favoring it 5 years later. The cases are different. It's entirely possible to give a seemingly pro-abortion ruling if the laws of that state are clearly in favor of it. Parental notification laws are an example of this. A judge has to go by the laws of the state even if they disagree with them personally. To do otherwise would make him a judicial activist.
Republicans just want to look at the results of a few case - "she has ruled for the 2nd amendment several times and against abortion 3 times" - and try to use that as some sort of predictive tool. It's very naive, as the relevant laws must be considered in every case.