No matter who you are or where you are the fact that you may have a tough to terrible show is always possible. If you sense this is happening and you're just not getting the laughs you expect or have gotten before there are a couple things you can do.
First, by all means , don't panic and speed up. False energy and insincerity is detected by an audience like blood is to a shark. It looks like desperation. See through the absurdity! Realize that it will end in a few minutes and it's NOT the apocalypse. It can happen to any stand-up at any time. It's part of the reason we do it...the test!
Many times the reality is the audience that we're bombing in front of isn't in on the fact we're bombing....only YOU are. The audience has been told it's a comedy show...that's about all they know. They have zero clue how many laughs per minute you usually get or think you should be getting. Why let them in on it?! Just keep moving forward and keep your material as fun as you can.
If you sense it's the material they are not buying switch up some. Sometimes it's the material that makes your show and sometimes it's just you being funny. If the material isn't doing it try stopping and talking to the audience briefly, this will allow you to return to your material or change it up. Turn on the funny person you know you are. Make conversation with some people near you or talk about what you see in the room, this will break the vacuum of silence usually.
The most important thing in bombing is to learn from it. Ask yourself why it happened, was it a heckler that got the best of you? Was it a drunk crowd that just wasn't listening? Could you have made them listen? Did you make mistakes with starting with or continuing on with the wrong material?
Standup comedy is walking on thin ice no matter where it is done. Respect that. Come prepared to start strong and stay strong and be willing to use the 'tools' you have to present as good as show as possible.
*"If you lose the battle, learn the lesson".