This can be quite a daunting task, especially for a new OPC. One of the best pieces of advice is to start with later records and work backwards from (what should be) easier to decipher script.
However, eventually it's likely that all OPCs will come across a form of Early Secretary Script, or its equivalent, or even records in Latin. The illustrations and references on this page are intended to help with those.
A few of the illustrated characters below survived until well into the 1800s, so most transcribers will be familiar with the double s (which looks rather like a modern day fs) and the e (which looks like a crossed through o). Some of the others in this image are not so familiar.
Websites with other useful illustrations include:
2. A more complex set of examples from Cambridge University.
Clicking on 'Go to Lesson' will launch a pop-up window and it's possible to see
translations of each image by clicking on the symbol 
1. From Genealogy Quest, a list of frequently-found words and their translations.
2. A much more comprehensive dictionary from the Babylon website.
3. A similar glossary of words found in English records.
1. For help with deciphering records in Old English.
