Hey there
I'm assuming you're coming from a mainly "multiplayer world"
When it comes to replay making, style is important. You've got to learn how to make your hits look good, and it isn't just based on effectiveness. Kicks have to look like kicks and punches have to look like nice solid punches, not just random twitches here and there (Unless you're a pusga)
For starters I'd suggest starting slightly further away from Uke. This allows you to have some room to swing your arms about to gain momentum from an opener; you can watch some of the default replays to see what I'm talking about.
When doing things, make sure to have what you want to do in mind. For example, you want to think "The position I'm in is good for a kick so I'll do a kick to his chest" and then carry it out to completion. This helps to eliminate some of the problems you have such as randomly slapping or kicking Uke for no reason
Some terms to get you on your way:
Madman - A replay with 5 or more dismemberments
Boomhit (Boomkick/Boompunch) - Three dismemberments with one hit