Most likely you will have a sheet someone can give you that has the common remedies down one side and some areas at the top where you can write the symptoms. The computer repertory systems are similar so the principles apply.
When you write down the symptom at the top of the page, also write the page number of the rubric which will help you review your case later.
As you look up the rubrics in the repertory, you note the grade at the intersection of the remedy and rubric. Total up the number of symptoms covered by each remedy. You can also break it down to show how many symptoms per grade were covered also.
The highest total of matches with the most in the stronger grades will usually be the simillimum. But sometimes just knowing that a grade three symptom is so peculiar and works well with the mentals is enough.
Two strong remedies with close scores will require a study of the materia medica for other eliminative symptoms. It could be genetic, miasmic, or more likely a general keynote/constitutional characteristic which will lead you one way or the other. A comparative materia medica is very useful here. My favorite is Gross.
The best remedy will be the one that will match the proving of the remedy in both intensity and number of symptoms covered. I like to regard number of symptoms covered as the best indication of the value of the remedy.
Small remedies are not well proven and should be regarded highly if peculiar symptoms lead you to one. Larger remedies like the polychrests will always be strongly indicated because of the number of symptoms covered. You will get used to distinguishing whether you have a Sulph. case or not. Don't disregard them just because they show up often! They cure more often than others also.