You decide how much you are willing to pay for that job, generally there will be a range even for the exact same position. Shift leads, and supervisors will make even more.
You also decide on the job qualifications: X years doing this, y years doing that, education of Z.
Then you filter the resumes and applications. Ones that don't have the minimum qualifications or are way overqualified never get interviewed. At some point you will discuss salary, that might eliminate some others that need to make more than you are willing to pay.
Notice age was never an issue. If you want the employee to have 2 years of help desk experience using system x, they could be 20 years old, or 70 years old. This could be the start of their career, or it could be their second or third career just to make extra money.
In the US asking about some things is a red flag. You must have a valid reason for knowing a persons age before the hiring decision is made. Requiring that a bartender be over 21 is good, if they are there is no need to even interview them. Discriminating by age is wrong; but establishing before advertising for the position what the requirements are is acceptable.
Some companies will redact candidates names, pictures, names of colleges, and graduation dates from submitted resumes to make sure the people reviewing them aren't biased.