Interesting idea, though I think it's going to be more or less the same for every european country. It's just the USA that is very weird in this aspect.
So how do we vote in Portugal?
I don't know how it works for immigrants, but for all Portuguese citizens, the moment you turn 18 years old, you are automatically enrolled in the voting lists of the parish where your official address is. Parishes (Freguesias, in Portuguese) are the lowest level of public administration here, corresponding roughly to a village and surrounding countryside or to urban districts in cities. They are direct descendents of the catholic church parishes of the 'Ancien Régime', before there was a proper state with a writen constitution. When you move to a new place, you have the option of changing your official address. This address is registered electronically in your citizen card, and by changing it, you automatically enroll in the voting lists of your new home parish.
A group of parishes constitutes a municipality, the middle level of administration, usually corresponding to a middle sized city and surrounding areas. Lisbon and Porto grew way beyond the limits of their municipalities, so the municipality only corresponds to the "city center" of each metropolitan area.
Excluding the autonomous regions of Azores and Madeira, which have their own governments and elections which I don't know that much about, we have 3 types of elections.
Autarchic elections, Legislative elections, and Presidential elections.
In autarchic (local) elections, you vote for the parish assembly, the municipal assembly, and the municipal council (the mayor and his team). In all these categories, both parties and independents can file lists of representatives (deputados). The municipal council is the only executive body directly elected in Portugal. The parish council is decided by the parish assembly, i.e. the party/independent list that has over 50% support of assembly members forms the council. Autarchic elections happen every 4 years (next in 2021).
In legislative elections, you vote for the Assembly of the Republic (the parliament). Only political parties can present lists of candidates for the AR, no independents allowed (which sucks ass, imo). The government (administration, for our american buddies) is then nominated by the President considering the party/coalition that commands over 50% of the AR. Usually, the leader of the largest party in the AR becomes Prime Minister. Although we don't have an electoral college type of system, we naturally have electoral districts. Each district elects a number of AR deputies proportional to their population:
This means that in smaller districts, votes for minor parties end up being "wasted", since the largest two parties divide the 2-5 deputies roughly in half between them. Nonetheless, when pooling the total votes, the AR makeup is quite close to the vote % each party got nation-wide, thanks to the large districts making up for this flaw. For example, last year, 3 parties which barely got over 1% of the total vote elected 1 deputy each in the Lisbon district. Legislative elections happen every 4 years, if the government holds enough support. If the government is dismissed, a new election may be called by the President before the scheduled period.
In presidential elections, you directly elect the President of the Republic, a largely ceremonial position, but which also holds just enough power to sway and influence the government sometimes. Any citizen above 35 years old can be a candidate, as long as they collect 7500 signatures of support. Naturally, political parties present their candidates and try to get one of their members in that position as well. The President's tenure is for 5 years and the same person can only be elected twice in a row. In this election, there are no electoral districts or anything like it. The total votes are counted and whoever wins over 50% becomes president. If no candidate reaches 50%, a runoff happens between the two highest voted candidates, although this only happened in 1986 (but it was a massive dramatic comeback that remains historical).
Election day!
When it's time for each election, as I said, you're automatically registered to vote in your local parish. You just need to confirm where exactly is your voting station by sending a text message or visiting the electoral registration website and entering your ID number and birth date. You can only vote on that one station.
Each station has 5 volunteers in charge of the process. When you go to your station, they check your citizen card and state your full name out loud to see if you are on the voting lists. If all is correct, they check your name on the list and hand you the ballot. The ballot is a piece of paper listing all the candidates, like this:
You take it behind a booth, write an X or + in the box next to a single candidate, fold it twice, and insert it into the ballot box. If more than one candidate is selected, the vote is considered null. If anything other than a cross is written, it's null. If the cross is outside the respective square, it's null. It seems pretty simple, but I've counted votes before and there are lots of idiots who can't manage to do it properly…
How do we count votes?
After the voting sections close, at 8 pm, the 5 volunteers who oversaw each section open their respective ballot box and empty it onto a table.
Each person is given a sizable bunch of ballots to separate according to the voted list, if they are null, or blank, into different piles. Then each pile is counted by that person and at least one other person. The counts of all 5 persons are then summed up and registered. Each pile is sealed in a special envelope, along with the resulting count, and sent to the responsible court.
The whole process, from registration to voting and validation, is overseen by the National Elections Comission, an independent organization associated with the Consitutional Court and lower courts, ensuring the process follows the same rules and standards everywhere.