Numbering measures will help save time and confusion when you get to Summertrios.  People have different editions, so you need a way to quickly and unambiguously locate a starting point as you rehearse.  Otherwise you waste precious rehearsal time while people fumble around trying to find the right place. There is no exact standard for numbering but if you do it as recommended below, things should work out:

General Rules

Count the beginning of each measure.  Do NOT count partial measures at the beginning of a movement.  Be sure to check the number of beats in the beginning measure to see if it is partial or an entire measure. Be careful not to count a measure twice, for example if it is divided across a change of key or clef. At a repeat with first and second endings, do not count the first ending.  Count only the last ending. Sometimes there is a change indicated in the order things are to be played: a trio, a coda, etc.  Number these measures consecutively with the body of the work.  Do not start over at 1.  Remember that we are trying to identify measures here, not necessarily follow the flow of the music. Number each movement separately.

Special Situations

Numbering properly is hard to do.  The best approach is to number the score and at least one part with it.  If you come out with 344 measures in the score and 346 measure in the part, something is wrong. Frequently a repeat is indicated in one part and written out in another.  In the part that is written out, re-use the numbers from the part that has a repeat indicated.  This is why it is wise to do numbering with the score and the part.  Otherwise you may be unaware that this discrepancy occurred. Discrepancies between score and parts.  Number as per the score. Cuts.  Sometimes an edition will omit some measures, because although they were originally in the score they are commonly cut.  This will result in confusion in the group if people have editions with different cuts.  The group will have to decide which edition it is working from, and you may be to renumber your part accordingly.