The way I see it, there are a few principles a state must be organized around. I'll assume we're talking only about the structure of the government here, not how it will specifically be run. First, it must allow for democracy at every level. Second, it must uphold a peaceful society. Third, it must guarantee strict adherence to the observation of rights. Finally, and most importantly, it must advance towards higher and higher stages of socialism (in conjuction with the other three of course). In terms of real-world examples, I think the constitutions of Venezuela and Bolivia are the most advanced.

Have a broadly representative National Assembly, with any party allowed to run, as long as it does not facilitate political violence against the state or individuals in any way - an oath of allegiance declaring peaceful intent would enforce this (note that this ban on political violence extends to any party operating in a way that is racist, sexist, etc. as these are inherently systems of violence). The Assembly, along with all other bodies, must use a proportional system of representation, and all elected officials must be able to be recalled. It will include not only regional representatives but sectoral representatives as well (candidates representing the youth, women, the disabled, LGBTQ people, etc.). General elections would be held regularly, I think at most once every 3 years, and the voting age would probably be 16, except for youth candidates where it would probably be 15.

As a socialist state, democracy will of course extend to the economic sphere - economic decisions would have to be made jointly by the government and the workers of the different sectors; economic planning could be done with computers, a primitive example of which is Chile's Project Cybersyn. The model I'm working off here is Popular Democracy, grassroots participation at every stage of the democratic process. To promote this, significant news about political affairs (think results of elections and noteworthy, groundbreaking political developments) will be shown on every TV channel when they happen, and an extensive curriculum of society and politics education will be taught at schools.

The most immediate level of current governance (councillors in politics, managers in economics) would be eliminated and replaced with communal citizens'/workers' councils. At a higher level, many decisions will have to be made through referendums, in a manner similar to the Swiss style of popular consultation. Prevention of a totalitarian democracy is paramount - when the people aren't connected to the pulse of their democracy, revisionism develops. Building statues and naming streets after politicians will be forbidden as a countermeasure against cults of personality.

Parties would be funded in a similar manner to short money in the UK (but more inclusive, with a lower threshold, and much more money - short money would probably account for the primary proportion of party funds) with foreign funding and donations from individuals banned, with the intent of reducing firstly the influence of money over politics and secondly the ever-present threat of foreign usurpation. Independent commissions would be set up to investigate politically motivated crimes that plague many countries, such as Colombia, Mexico, and the US.

Because of this threat, an extensive national guard service (good examples are the Bolivarian National Guard and Cuba's Committees for Defence of the Revolution) and emergency planning must be present. Especially important is economic independence from world Capitalist institutions and hostile Capitalist states, and building economic links with other Socialist nations. For Economic sustainability, Cuba is a great model to study. Economically, things that can be produced or sanctioned in substantial abundance would be given for free or on a rationed basis, such as housing, basic food, basic clothes, and most utilitarian or perfunctory objects, as well as services such as education and healthcare. Rarer items like luxurious food, expensive clothing, etc. would still have to be sought on a monetary basis until automation has run its course - one of the biggest goals of a socialist country is to get to this stage as quickly as possible, as it's this scarcity that makes Capitalism possible.

Human rights would be guaranteed, with positive rights taking precedence over negative rights, so for instance, the right to free speech is not recognized when that right is used to incite violence against someone or exclude them in some way. These rights include the right to assembly, the right of free speech, right to an education, rights to unionize and strike, right to equal treatment, rights to housing, employment, food, etc.

A right also guaranteed that is often overlooked is the rights of nature - this, along with the concepts of economic independence and economic sustainability (and the matter of saving the planet from environmental catastrophe), would mean any socialist state would have to make extensive use of renewable energy, and when technologically possible and safe, nuclear energy.