You have to do your due diligence and research what MOS you want, and if you qualify for it (especially if you have to have a clearance, particularly a TS clearance). The career counselors will offer you what is considered hot, or high priority slots first; when I came in, it was infantry, transportation, and armor (both scout & tank).There are, at times, quick ship bonuses that come with these jobs, provided you can basically pick up and go within 30 days.
If you've got a job that you have in mind, and they don't, and maybe won't offer you, kindly thank them for their time and explain to them that you are looking for a specific MOS. I've seen recruits go three or four times before they were finally offered what they wanted.
The other biggie is that if you have a college degree, DO NOT let them talk you into becoming a Specialist as opposed to becoming an officer. It's not just a difference in pay, it's a complete difference in your quality of life you're allowing them to determine for you.
If you have a degree in anything related to healthcare, ask for the region's Army Medicine recruiter info as they, the AMEDD recruiter will ensure you're taken care of.
The choice to serve is an important one that I commend you on. Please, enter on your terms as to ensure you do not regret your choice.