Suppose you have one part-time job . . .

[Nikia]

2. You should be honest but I have known a few people who have had problems with this

If they worked in retail, for example, they were told that it was unacceptable to have another retail job or if they worked in a restaurant that it was unacceptable to have another restaurant job because their loyalty was in question.
If either job has hours that are flexible at the employers discretion, you have to make sure that both places will work with you to work around your schedule. Even if a business does not expressly say that they are unhappy that you are working another job, they can use the schedule to make it difficult or impossible for you to keep both jobs.