Almost everything that makes a beginner better in the first months is consistency rather than power. The ball crossing the net ten times in a row beats one shot nobody could return, and it is worth saying because the second is more fun and the first is what wins points. A coach will usually start with where you meet the ball and where your feet are when you meet it, long before anything that looks like technique.
The most useful idea to carry onto a court alone is that the ball goes roughly where the racquet face is pointing when it makes contact. A great deal of early frustration is a face problem being solved with more effort, and effort makes it worse. Slowing a swing down until the contact repeats, then adding pace back, is the loop that most improvement actually comes from.
The serve is worth its own attention because it is the only shot nobody else influences. Nothing arrives at you, nothing is rushed, and the whole thing begins with a toss you can practise anywhere with no court and no partner. A toss that lands in the same place twenty times makes everything after it repeatable; a toss that wanders means you are inventing a different serve each time, which is why the second serve is where inconsistency shows up first.
Where coaches genuinely differ is the grip a beginner should serve with. One view starts you on a grip close to your forehand, because the ball goes in sooner and confidence matters early. The other insists on a continental grip from the first lesson, because it is what a real serve is built on and changing later costs more than learning it slowly now. Both are taught by good coaches and the trade — early success against later rebuilding — is the actual decision, not a right answer.
None of which is a substitute for somebody watching you. A coach fixes in one session things a paragraph cannot even describe, because they can see what you are doing and this cannot. Take the ideas above as what to expect and why it matters, and let the person on court with you have the last word.
General guidance, not a research finding.