Build up a systematic approach to how you handle issues. Wasting time by blindly trying to apply fixes or giving an issue the wrong priority are pitfalls you want to avoid.
Make sure you understand the issue before you do anything. If the information provided is unclear you go back to the user and gather the necessary information. Information like:
Steps to reproduce: what are the steps to trigger the issue. This is important for you or others to understand and reproduce the issue. Also if you can't reproduce the issue then you can't confirm if any applied fixes solved it.
Number of users affected: is it a local issue or a general issue. This is important to understand the impact of the issue, where to look for the issue and what kind of priority to give the issue. If a user says everyone at the office is having the issue then you can skip trying to poke around on that one user's machine and escalate quickly if you can't figure it out (many users impacted likely impact operations in a costly way).
Screenshots, frequency and timestamps are also very helpful bits of information, especially if you have to escalate. Also always gather this information even if you know early on that you have to escalate. Someone more experienced and skilled shouldn't waste time gathering the information when you can do that. They will also very much appreciate that you did a proper job and would be more willing to share how they solved the issue.
Contact details. Don't trust the company's people directory or details from Active Directory. Verify the phone number where you can get ahold of the user if needed.
You need to be less concerned about not knowing the answers and more concerned with acting on an issue. If you don't know how to proceed the worst you can do is freeze or go idle. Ask someone for help. But yes, many times you won't even know who to ask. Build up your own contact lists and force yourself to find out who to contact for specific systems, subjects, etc.
If you have any sort of natural excitement for IT and want to learn, then you will do fine and hopefully keep your ambition up to gain knowledge and experience that can open new doors. Good luck.
