This is a contribution by a tournament broadcaster and MWO community member, BanditB17!
How To Find a MechWarrior: Online Unit
One of the most beneficial steps a new player can make in MechWarrior: Online is to join a unit. Units provide a whole new level of gameplay and social interaction. From veteran pilots who can provide a wealth of knowledge to the bonds of friendship that can grow and exist outside of the game units improve the MWO new player experience significantly.
Units can come in several shapes and sizes. Some are strictly casual while others are very competitive with mandatory practices and events. Some play Faction Warfare while others focus exclusively on 3rd party league play. Some are very large with hundreds of players, and others are very small but active.
There are several methods to find a unit that is the best fit for you.
Unit Advertisements on Faction Forum
Units will typically have one post in the subforum that fits their unit the most, whether it be a merc unit or faction loyalist. You can read through the posts to see what each unit has to offer and they will typically include a link to their website to apply.
Hiring Hall
Make the units come to you! Many recruitment officers for various units will be notified if a pilot posts to the Hiring Hall. Post a short blurb about yourself and what type of unit you are looking for and your inbox will fill up with personalized messages from units that are hiring.
Reddit Recruitment Threads
Units that have a presence on Reddit will typically contribute to the recruitment thread. Some of these units tend to be a bit more on the competitive side, so if you are looking for a bit more hardcore experience I would start here.
MRBC League Tables
If 3rd party competitive league play tickles your fancy, most of the teams listed in the last season of MRBC are most likely looking to grow their rosters. Clicking on any of the teams will take you to a page with a description and method of contacting the team. Teams are divided into divisions based on skill level. Higher division teams may have more strict experience requirements to join.
House/Comstar/NGNG Teamspeak hubs
There are almost always groups forming in the common areas of most house and community hubs.. Simply dropping with others allows you to network and potentially find a unit through a fellow pilot.
Looking For Group
(In-Game)
Using the LFG feature in the game, you can start dropping with other people right away. You can network here as well and potentially find a unit through a fellow pilot.