For Hilton and Conrad you need to make sure your My Way preferneces are set to free breakfast. Be aware that it is only contenental breakfast but in most places this is good enough and saves money. Some hotels will give a full breakfast but do not have to.

You will not see anything about this when making the reservation. The hotel will look at your chosen My Way settings and take it from there. Follow the link 3Cforme gave to see what the benefits give, then go to your account and choose your preferences.