Providing you have got some identifier which uniquely identifies a person (eg personind as an autonumber), and that identifier is used in both tables then it should be fairly easy to do
suggest you create a new query, using the query wizard select the 'find duplicates wizard'
you problem is going to be if you do not have a simple identifier but rely on surname and forenames.
BTW the way it may be worth while considering merging the 'camper' tables into one entity, storing an additional column which identifies the year. The reason it gets round problems such as these. Granted it may not be appropriate in your particular case but generally speaking in its not wise to store what effectively is similar data in seperate tables. As an example, what happens if the marketing people want to offer a discount to or ssurvey people who have come to 2 out of the last 4 years, or analyse attendance on particular weeks or particular courses over time. When you need to look at a particular years data then it can be easily extracted from the table using a year paramter in your querires.