How to turn an internship into a full time offer?

Try your best to impress in the same way an intern usually would (be evaluative - i.e. ask interesting questions, be goal-orientated and have strong attention to detail, etc) then pounce at the first "relevant" opening that pops up at the firm. Speak to your superior before applying. I stress the importance of relevance because you should have identified your area of interest at the outset of your internship

A lot of people have been mentioning that its good to set up coffee talks or chat ups with senior people in the company to network but surely that would be annoying for them? Or is that normal.
Sorry, new to this professional setting networking so yeah :/

I found the best ways to get a return offers was to just generally make the life for your team easier. You should be doing something called upwards management. Ultimately if you're a decent enough person, can do the work and make your team's life much easier then they're far more inclined to go to bat for you when all the seniors get together to discuss which interns they should give FT offers to.

Beyond this, be confident but not cocky, under promise and over deliver and just generally be kind/friendly.

With regards to networking, if you're in the office then you should be using your spare time to subtley and sometimes overtly network. So going for drinks with coworkers really helps to build rapport and for them to spill details, just don't get beyond tipsy. Asking people for coffee's and catch-ups is completely common practice. If they've got time, people are generally very open to sharing advice or spending 15-30mins chatting to you, they're more inclined to do this if they like you and you're at least competent.

Beyond this I try to get a sense of what the internship will involve as much as possible so that when you start you can hit the ground running. Managers tend to give interns a bit of slack so if you show you don't need it then they'll see you as saving them time rather than them having to waste time on you

Yep, networking internally with your seniors is an extremely good approach to take.

Opportunities may arise very frequently and it’s up to the business to make their interns aware for these openings.

I would interview and take notes for the future and even attempt to mirror if you are dedicated to that particular company.

Don’t be too much of a pest towards them though please, your Directors and C-Level people are very busy people.

Really appreciate the insight guys, THANK YOU