Parties negotiate to form a majority coalition, or a minority government with a confidence-and-supply agreement from other parties.
In Proportional Representation, usually it is the party who has won the most seats in the legislature (or, the most votes in the event of a tie in the number of seats) will lead the formation of a coalition.
The Speaker of the house is chosen by a vote of all MLAs. Any MLA, from any party, can put their name forward for the position.
In a coalition government, or in the event of a tie between the two largest parties, it is common for the speaker of the house - who does not vote except to break a tie - to be chosen from a the opposition or minor-party benches. This gives a one-vote advantage to the governing party or coalition. The 'opposition speaker' scenario happened three times in Canadian federal parliament, even under First Past the Post.
In countries that have proportional representation, the most common form of government is a majority coalition government: an alliance of different parties, none of which could hold a majority on their own, agreeing to cooperate to form a stable government with a clear majority of the seats. The cabinet is then formed to include representatives from all coalition parties, which encourages transparency, openness and true debate.
Confidence-and-supply agreements (such as in BC and New Brunswick in the last year) can also deliver stable minority governments.
Under the current 'Winner take all' system, single-party majority governments form too easily - often, the party in power hasn't even earned 50% of the popular vote. The cabinet then consists of the representatives of just one party, meaning powerholders make decisions behind closed doors, with no need to be transparent.