The practice starts with directing those good vibes towards yourself for we can all be too self-judgemental at times. Even though I'm far more self-forgiving than I ever used to be I still need to be reminded not to be too hard on myself as an erring human. After becoming still and focusing on the heart, words along the lines of the following phrase are repeated.
May I be safe, happy and well. May I be peaceful and at ease.
The same sentiment is then expressed in turn about a loved one (Louis!), someone neutral for whom there's no particularly strong feelings and then a person where the relationship is difficult. One talk I heard was very clear that you only needed to bring to mind a singular individual who had pee-ed you off. You don't have to think of everyone who's been hurtful, cheated you out of money or cut you up at traffic lights. Grrrrr! Just a solitary miscreant suffices as they will act as a paradigm, an example from which loving thoughts can be extrapolated to all those other bastards. You see I'm not there yet!
There's lots of free resources out there . Just have a little look on YouTube if you're interested. There's guided meditation and talks aplenty to whet your appetite. My favourite resources are a couple of long talks by monks, which incorporate meditation practice that have caught my fancy, this one by Ven Ajahn Sujato and another with the incredibly smiley Bhante Vimalaramsi.