When you're interviewing a possible personal care assistant, start with simple questions about a candidate's background and experience. Ask her where she's worked and what her work history has been like. What were her best and worst work experiences, and why?
That's a good way to get someone to open up. If she starts telling you all the things she had to do that she didn't want to do, or complains a lot about past employers, you can tell a great deal from that. Some people will say something revealing, like "I didn't like bathing people and changing soiled clothes." That tells you they don't have the right attitude. Others will start telling you what a wonderful experience they had caring for someone, and you can just feel the commitment. The most important thing is to find someone who has a real heart for working with older people, who isn't just doing it for the money.
Ask potential candidates about their comfort level with specific personal care tasks, such as whether they've worked with people with incontinence and have experience changing disposable pants and other incontinence products. Ask them to describe how to give a bed bath. If they know this, they're usually pretty experienced. If they know how to change the bed with someone in it, that's telling. Ask if they have previous experience working in a nursing home. If so, they're likely to have had lots of training and experience with different circumstances.
If you want the personal care assistant you hire to cook, ask her how much she cooks. It doesn't matter so much if she has professional experience cooking or what kind of food she makes for herself. If she's done a lot of cooking and is confident in the kitchen, she'll be able to cook whatever the client wants, even if it's not what she normally makes at home. She just needs to have a comfort level with reading and following a recipe, and that's not something an agency or training program can teach; that comes from time spent in the kitchen.