Alright, time to 'fess up (whatever that means). I have a guilty secret. I'm a word addict and not only that, I'm a word fetishist too. What's the difference? Well, an addict loves words and can't get enough of them, but a fetishist goes one step further and makes her own.
The great thing about the English language is it's such a mongrel of other languages. There are umpteen words for the same thing, each with its own unique and colourful derivation. In amongst all that melee of vocabulary it's dead easy to slip in a few made up ones without anyone noticing. (Of course you do get the occasional dictionary wielding pedant who calls you on it, but don't let that spoil your fun. They need to get out more.)
Now, if you're thinking of trying this I should warn you that making stuff up can get you into trouble. But unless you're a finalist in the World Scrabble Championships don't sweat it. It's harmless fun and very creative.
A good place to start is insults. In the heat of the moment folk seldom take much notice of the words you are hurling at them. Next time you're having a screaming row with your neighbour toss in the odd invention: Don't look at me like that, you scumsucking fenchmallow! At best it'll take the wind out of their sails, at worst it won't register.
Slipping inventions into your prose might be trickier although not impossible. The key is to keep it low-key and unobtrusive and don't get carried away. For example, The wind rustled through the venic leaves, lifting them to flutter in an exotic dance is better than The bartledick rustled through minaries of venic leaves, fletting them to flutter in a partsimious dance which even the sloppiest editor will spot a mile away.
So, start small and remember to enjoy yourself. Who knows, with any luck you might end up with a few of your inventions turning up in next year's OED. Good fetishing!