You mentioned knocking and clicking in your description, so have to be a bit more specific. If sounds like a metal knocking from within the engine, it can be quite a few things and a bit more serious.
If it's a clicking sound it can be mechanical or ignition related. Spark plug wire leakage will cause a clicking sound and will cause both engine shake and rpm drop.
Could be that the valves need a bit of adjustment as well.
Really hard sometimes to pinpoint some problems on a forum, best bet is to have a mechanic look at it.