Recruitment processes can be drawn out. Just because you have one interview first, does not mean that it is the first offer you will get (making the assumption you will be successful at all interviews).
Paper work for offers usually takes some time to be drafted and created. By the time it gets sent to you, you have some time to consider it and get back to them. You can informally and verbally accept an offer and state you will wait to see an employment contract - which will buy you some time.
If you do get an offer, you can contact the other organisations you prefer to see if they can bring their process forward. They might not be able to, but there is no harm is asking and saying to them you have another job offer that you need to consider.
You can also ask the first organisation who offers you a job some time to consider the offer. You don't have to make a snap judgement unless they need someone ASAP.
In the worst situation, you could renege on an offer or if you have started the job, just work your notice period. You probably won't be able to work for that organisation again (say you make the wrong decision and hate the job you do accept, it's unlikely you will be able to go back to the other offer and ask to be reconsidered), but that's a risk you will have to take when making a judgement on what is the best thing to do given your personal set of circumstances.
Job seekers have to deal with this type of situation all of the time, as do recruiters. The best talent often get multiple offers or are involved in multiple recruitment processes at the same time, so it is fairly standard for recruiters to be able to deal with this situation the best way they can. For candidates, it's just about using your own common sense and judgement on what to do.
Posted from TSR Mobile