Three questions about an accounting clerk job interview

I would like to know if the interview is extended you by the Employer directly, or if you are being interviewed by a recruiting firm. That would make some difference for the purpose of the interview, but not on the dressing.

For what concerns attire,
I believe that wearing a suit is not overdoing. I like to believe that is better to be overdressed for the occasion than under-dressed for the occasion.

For what concerns pay,
Here is where there is a difference.
In case you interview with the Employer directly, you can try to explain that you are willing to negotiate. Ask them what they have in mind, but if you can try to explain that you will be interested in discussing the details once a final offer is on the table.
HOWEVER, this depends with whom you are talking during the interview. If you are being interviewed by HR, then do your homework, and try to find information about what is the average pay for that position IN YOUR AREA, and possibly in at the specific company. Also you want a number that makes sense to the business but does not make you miserable and unhappy. If you are being interviewed by the hiring manager, then that question is in general something the could be happy with an answer such as "willing to negotiate". since they are about you fitting with the environment, and your technical skills.
If you are being interviewed by a recruiter, then all they want to know is what pay are you willing to accept. they interested in the lowest number you can be made available, In general, with a recruiter if you can name a range (between a<pay<b; where a,b are constant) then you would have answered their question.

For what concerns the kind of questions they will ask you,
If the company uses a very traditional approach, they will ask you the questions that are floating around since the 1950s. Tell me about yourself, where would you see yourself in five years, what is your greatest weakness, etc.
If they are up to date with the hiring process, they will try to have a conversation with you about work, ethics, and maybe some fun too.
I believe that it is far more likely to be asked the 1950s question because they have to put in less work, and reading a script is easier especially at entry level. Do some research on it, and what they want to find out about you through the "canned" questions, and you will be fine!

Best of luck with your upcoming interview, do your best and you will be fine!!

Oh! something important I wanted to say but this did not fit anywhere. If you do not know much about at-will employment, get up to speed as fast as possible. Also, keep in mind that when you sign anything, courts will be holding your signature as valid during a trial --hopefully you will never need it.
Try to understand what you are signing --especially if you are signing away your rights to vacations, overtime, intellectual property. Pay special attention to non-compete agreement (in general they will prevent you from working in a given field for a number of months/years and are binding).
You can take copy of what you signed and consult an attorney in case you signed something you did not fully understand. I'm not sure what good will it be after signing, but you may try to work out a solution, At least you know what you agreed too!

Best!