The others have noted that nominations should be made of those who the unit thinks may have something to offer to the order of the arrow. While not an honor officially, many still find it an honor to be asked to serve. My best advice is that you know the adults in your unit better than anyone else in your scouting community, and, you know there are some adults that don't need to be asked before being nominated, and there are some, that you think may have something to offer, but maybe you are not sure, ask them.
As a chapter adviser, I know I need adults with a couple of spare weekends and a couple more spare evenings per year. Right now, it is making sure that our elections team has transportation to troop meetings that aren't in their neighborhood. That our chiefs and those who serve on lodge committees have transportation to lodge meetings. I also need adults to help the youth get to fellowships & conclave as a lot of these events occur some distance away. I hope some of these adults can develop into advisers for various chapter committees, such as, elections, ceremonies, dance, etc. as one day, the current adults filling those roles will move on and we will need someone to fill their shoes. I also need a finance adult, it is something that I'm not very good at myself, budgets, balancing, etc. I think it would be really helpful to have someone with a background in that sort of thing to help the youth in charge get a handle on these budget things.