Hi Jupiter,

The differences you may notice from being in a worship service could vary from congregation to congregation.  Sometimes there are bigger differences between congregations of the same denomination than between any of the ones you noted.

Beyond that, they each have very different histories, and organizational structures. 

UCC is a congregational structure.  The local Church makes all their own decisions, so you should expect a lot of differences between congregations..

Episcopal USA and most ELCA use a worship pattern developed by their denomination, but the style of worship and theology can vary, based on the congregation.

The United Methodist Church is a blend of all of the above.  There is only a recommended order of worship, so you may find very different styles of worship from congregation to congregation (like UCC).

Each has a website that you can explore.