Practice good posture, mouth shaping, pronunciation, breathing, tonal quality and good resonant quality while singing. Usually this entails standing up tall and straight (don't puff your chest out), singing loud enough so that your singing doesn't sound airy unless that's the effect you want, forming the words with your mouth and pressing your tongue up against the back of your bottom teeth for some vowels (although not so much so that you sound like the village idiot)
For acoustics, you'll probably want a pop filter if you don't have one already, a condenser microphone is recommended but a dynamic can work as well, if you don't have one of the
acoustic shields for your microphone, and don't have any regular acoustic panels you can put up behind your mic temporarily then try to stay out of corners and small spaces so that the mic doesn't have any ringing or bad reverb response.
Mixing the vocals can be pretty crucial. Use compression to either add or remove dynamic range as you feel is necessary to carry the emotion you're looking for, EQ out any unnecessary frequencies that may come as a result of background noise or whatever, and maybe some reverb to add some lively-ness to the vocals, although the amount you add should be relative to how deep in the mix you want the vocals (more will send the vocals to the background, less will bring them to the front)