Basic Encoding Rules
Basic Encoding Rules or BER 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.
BER is the most flexible format of the encoding rules. Slightly more stringent is CER, with DER being the most stringent. ASN.1 also specifies syntax for XER, or XML encoding rules.
Viewing and Editing Tools
Peter Gutmann's asn1dump is the command line tool of choice for viewing certificate encodings.
There are plenty of visual tools to view a certificate, including online viewers.