When choosing to attend a conference be aware of the following:
Individual conferences will have individual publisher/author agreements which you will need to comply with. Check these for open access policies.
Large professional organisations, such as IEEE, will have a clearly defined policy stating which version of the conference paper can be made available in an open repository.
Legitimate conference paper submissions will include a peer review process, so be wary of those that do not.
Predatory and fake conferences are organised by for-profit companies. Avoid these as they may be money and time-wasters, and may restrict your ability to publish your research in legitimate forums in the future.