Well I don't want to be the host myself. My connection here sucks. I just want someone on my team to have it. You can tell this by how the people enter the room in the lobby. Usually, if there are empty squares for people to enter before they do, someone on your team has the host. If a group pops in the room all of a sudden then they have host.
Like skate said, you can see if you are host yourself by grenade jumping and that other method of holding right on dpad for blue is also true.
Another easy sign to know if you, yourself is the host, is when you pick up the overshield. If it levels up evenly then you are hosting. If it just appears or is choppy filling up, then you are not hosting.