I don't have any plan per se. Depending on their performances and development, I start off my hot prospect youth in Capital One Cup games, FA Cup games and FIFA Club World Cup. You can easily win in those competitions with youth, especially since they're against lesser opposition, provided you have a couple of experienced players in the team.
That easily makes around 10-15 games a season where my youth play for the first team for the whole of 90 minutes. This helps in their development quite a bit.
I play them as substitutes in the CL only and only when they're around 19-20 years old and have developed well. I won't have to register them too by that age, making it less of a hassle.
In the BPL, at around the same age, they're present in my subs. Since my first team is outstanding, my subs usually consist of one vital first teamer, the rest being well developed, good prospect youth, who are good enough to play for around 15 minutes of so.
The selection of youth depends on their performances for the Reserves, and their performances in the Cup Games. Eventually, if a youth prospect is playing exceedingly well, I sell a first teamer and replace him with the prospect.
While selling a player (first teamer or lesser used youth prospect0, I'm ok with selling them for a lesser amount, provided they're having a 50% sell-on clause, which will be more useful most times than a slightly higher transfer fee.