This post is for the community to post/read up on tips and tricks made or found by other halo reach community members or just halo reach players in general.
Any tricks or tips out there for the hologram? I gotta admit I bomb with it (as in suck) but im going to try to get better with it. So again any tips or tricks?
Wait in a “hidden” spawn point and send it out, looking like you spawned and are walking forward… Then when they go for it, easy assassination 
I use Hologram all the time. It’s probably my favorite Armor Ability.
You can use it whenever you don’t think anyone will see you send it out and hope it works. It all depends on if they’re expecting it or not. Also, try to stay pretty close to it since it doesn’t appear on the enemy’s radar. It’s best when there’s a lot of chaos (like in Rumble Pit or Multi-Team) because there’s too much going on for them to realize it isn’t real.
One of my favorite things to do on Asylum is, as soon as the game starts, send a Hologram right down the middle of the map (towards Sword spawn) and see if anyone goes after it. If you’re lucky, they won’t realize it’s a Hologram, and you can get a First Strike because of it.
Hope that helps. 
With hologram use it to lure banshees in on invasion slayer on boneyard if your team it getting whipped (did this today, 2 boards and we lost like 100 26 or something…) if they go in to far board.
Also, use them for making sure a way is clear.
I guess you meant in matchmaking, but in the last mission in Campaign on Legendary, I used it to take out the three Elites in the last room.
I sent out the hologram, and then assassinated the Elite, repeat twice.