We can see the train bearing down on a crowd of people packed upon the tracks, but real action won't happen until it plows through them. If then.
I think our best hope of a world government will grow out of that growing conglomeration, plus diplomatic relations between such groups. I think that is our best hope because emergent (bottom up) solutions seem to generally be far more solid answers than top-down solutions.
It's the one people talk about most because it's the one with the most actual integration and power. The others are much looser.
People are hesitant to usher in a global power because nobody in the elite circles of such a power would bother listening to the concerns of the far removed people affected by their laws, it's more likely they would just implement ideology they think is best and become a prince ruling over a colony.
If anybody knows of any universities with an active political theorist department or journal that isn't recycling 20th century ideology I'd be interested.
1) You create a non-profit organization and hire a few people.
2) You create a website where every law proposal that goes through parliament/congress/whatever is displayed on the website, and you give each citizen one vote on this website on each proposal.
3) Your people run for members of parliament in the next election.
4) Here's the kicker: You promise that all of your elected members of parliament will unanimously vote on each decision whatever the vote on the website was. If a majority of citizens voted yes on a law, your people will also all vote yes and (hopefully) pass it.
5) Citizens are incentivized to elect your MPs because they are basically direct democracy, transparent and accountable.
6) You explain each proposal in layman's terms, and how it will affect people, so they're more informed on how they vote.
The good thing about this is that it's backwards-compatible with democracy and it's in the people's best interests to vote for your people. They do need to trust that you'll do what you say, but standard checks and balances apply there (you won't be elected next term if you don't). You also need to solve the electronic voting problem, which is hard, but this protocol is probably better than the one we have now where MPs vote based on lobbyists.
Where I am, a very vocal minority are involved in politics. A small majority are dispassionately interested in the workings of the government, and only vote on things of particular interest to those individuals. The rest couldn't care less, because they assume their one lone voice won't make a difference.
The internet (aka people) is why we can't have nice things, and will most certainly ruin this idea.
1: http://mentalfloss.com/article/52524/15-polls-hijacked-inter...
Increased access to information and decentralized media allows people to see the potential (and often real) corrupt nature of centralized power, so this isn't that surprising. When you coalesce power into a centralized entity, you remove accountability and provide perverse incentives to those who wield power.
It's a natural consequence of faster and more free trade of information, goods, migration of peoples, etc.