Basic Encoding Rules
BER or Basic Encoding Rules is a transfer syntax defined by the ITU in X.690. It is a Presentation Layer protocol which allows applications to exchange information. ASN.1 includes cryptographic extension which allows peer to peer encryption between applications.
Viewing and Editing Tools
Peter Gutmann's asn1dump is the commandl line tool of choice for viewing certificate encodings. Gemini Security Solutions  offers a visual front end to asn1dump.
Objective System offer a visual ASN.1 editor , which allows viewing and editing of a certificate similar to a binary hex editor.