How do I make the right move after an opening? I'm slowly getting better at my chess skills.  

The one thing that bugs me the most right now is knowing which piece to move after many of my pieces have been developed and the king has been castled.  

Any move I make after the opening either seems trivial or will lead to 1-to-1 sacrifices. I'm trying to understand what approach I should follow after both my opponent and I move up our pieces to the point where we can no longer any with sacrificing them in a way that gives me an advantage.  

Usually with beginners, they make some silly move so it's easy to know where to move my pieces. But with intermediate people I find it difficult to follow a consistent strategy after the first 10-15 moves.  

I tried to use a chess helper to determine the next move, but couldn't quite understand the pattern and the moves it made felt arbitrary.
Usually each opening consists in a middle game plan rather than just a sequence of initial moves. This means that the criteria behind choosing this or that other opening must be driven by the specific middle game positions that one wants to achieve or is confident to play (driven by personal taste, skills or whichever other reason).

There are mainly two ways to develop sense of positions for middle game:


studying the opening thoroughly: this means taking a book written by experts on the subject analysing positions very deeply until the endgame. Classical openings (Ruy Lopez, Queen's gambit, Sicilian, King's Indian) are easy to play but extremely hard to master, therefore one cannot really play them without extensive knowledge (unless you want to fall back into your previous case, where players end up moving pieces randomly after a while)
looking at classical games by classical players: this is the evergreen advice but really it does help to understand what to do. Good players are such because they have a sense of how to treat specific positions and come up with sensible plans for the initiative. In general looking at GM games helps understanding how to convert small advantages into winning positions (at the end of the day, chess games are not won by throwing all your pieces at the opponent's King, rather by accumulating small advantages throughout the game and converting the resulting endgame position).