Except for buying the most expensive tickets, there's no option to buy a ticket where you won't be "voluntold" to leave the seat you're already in.
What other option would you like? If you want a cheap ticket be aware of the fact you might get bumped. If getting bumped isn't OK then buy a more expensive ticket. Ya a first class ticket costs a lot more but in addition to complimentary alcohol you are less likely to get bumped. If getting bumped is a big deal then the cost of the ticket probably isn't.
The other really important thing to remember is that as good as the industry generally is at getting people to their destination at about the time they say they will there is always the possibility that there will be some issue that prevents you from getting where you want to be when you want to be there. It could be weather, or mechanical, or airport shooting or... If you absolutely have to be somewhere on Monday morning you shouldn't be flying on the last flight out Sunday...