How do you manifest 'properly'

I'm looking to manifest my dream job in a different country using the gateway tapes and this is my first time trying to actively manifest anything. I've read that if you try to rush it, you might get your wish but you might also get something unwanted along with it (e.x. you ask for money, so your house burns and you recieve insurance money). So my question is how do you guys properly manifest, and also if you're visualising something, how do you keep any negative visual from coming in between like you having an accident of something. (Hope I'm making sense)