Before a match, both players must select a character to use and a Kameo to provide assistance in the fight. The Select Screen is shared by both players, which means players can see their opponent's cursor and who they select. At times, a player might wait until their opponent chooses a character before selecting their own. This is what's typically known as counter-picking, as there are characters who are able to counter others depending on the match-up. To avoid this, a player can select the option to hide their cursor, preventing the opponent from seeing who they picked. This however requires memorizing where each character is on the select screen and carefully moving the cursor to the correct position.
Once a character and Kameo is chosen, the player is locked into using that character and Kameo for the remainder of the set, unless there is a rule in place that allows the player to switch. Depending on the rules in online Ranked mode or in a tournament, a player may be allowed to change their character and/or Kameo if they lose a match. If a player changes characters, some rulings even allow the opponent to change their Kameo despite winning the previous match.
Next comes the stage selection. It normally doesn't matter what stage is picked, however some stages may be larger than other stages and could potentially be better suited for certain characters. For instance, a character who relies on keeping a distance from their opponent will probably prefer a large stage where they can continuously move backwards, while a character who likes to stay up-close will want to play on a small stage.
Each stage also has different versions to choose from, such as a day version and night version. These can be unlocked through the game's story or Invasions mode. There usually isn't much or any difference between each version of a stage besides aesthetics so choose whichever version you like most. If stage selection isn't important, then you can simply pick the first stage your cursor is highlighted over since it is automatically chosen at random. Alternatively, selecting the box containing a question mark in the bottom-right corner will also randomly pick a stage.