Suggestions for giving or receiving a toast:
The host of the event should have the opportunity to toast the guest of honor first before others share their toasts. If it appears that the host has no intentions of offering a toast, quietly request the host's permission to do so yourself.
If you are able you should always stand when offering a toast unless it's a small informal group. Standing helps you get the audience's attention and settle them down. Avoid tapping a glass to get the guests attention as you could easily end up with nothing to toast with.
Not everyone is comfortable with public speaking. Insisting that someone make a toast could make the very uncomfortable.
Stand up and respond toast even if it's just to say 'Thank you'. You should wait to drink or stand up until after the toast is finished.
You should always participate in a toast although it's perfectly acceptable to do so with a non-alchoholic beverage.