Do look for a chance to announce yourself when you join the call. Do state your name when you make a comment or ask a question. Some class leaders encourage you to just speak up whenever there's a break in conversation, but others will ask you to press a key on your phone when you have a question or comment. This generates a brief tone and is just like raising your hand in a traditional class. Don't breath into your mouth piece.
Some phones are quite sensitive.
Don't use a speaker-phone. The quality just isn't there, either for your listening or for others to hear your comments. Don't use a cordless or cell-phone if you can avoid it. The sound quality is getting better, but most are not good on bridge calls. Click Here to reserve a bridge for your group or organization.