PSA: Calling for reports is itself reportable as toxic behavior
Right now on the front page alone there are 4 threads in which people asked for reports and don't consider that poor behavior, and I know it's a common thing to do (regardless if the report is deserved or not). So here's a quote from Riot Hursker:
Calling for others to report a player is a punishable offense. It is a form of bullying and as such is against the summoner code. It should always be a personal decision for each player as to whether or not they feel another player warrants a report. In fact, do feel free to tell your team mates that "report calling" in itself counts as harassment. Flaming and bullying a player will never help them to improve their game mechanics, communication etc.
So if you ever feel the need to say stuff like "x9 this guy" or "report X pls", don't. It counts against you more than against them, and it isn't even needed. What matters is the number of games reported, not the amount of reports per game, so 1 report is as good as 9. If you see somebody behaving in a way you feel it should be reported, report them at the end of the match. That's all. If they are indeed in the wrong they'll be dealt with with your report alone. Getting more people to report somebody won't change anything for them, but it might count against you.