it's all greek to me...
Well, of course it is.
That's nothing to be ashamed of.
Firstly, don't approach Shakespeare as you would a modern English text.
You will only be disappointed that you don't understand more of it.
Approach a Shakespeare text as if it is written in a different language:
this way, you will focus more on the 90% you recognise rather than the 10% that you don't.
Secondly, look at how many of the words you know.
It will be most of them.
Or at least, there may be similarities or root words that can help you have a good guess.
What often gets confusing is the order that Shakespeare uses them in.
Yes, sometimes you will have to refer to the glossary: but this is often true when reading any new author.
If you pull a tricky phrase apart,
there is a good chance that you can rearrange the words to make sense to you.
Another good trick is to 'translate' a sentence into modern English
and use this in your rehearsals as a 'gateway'.
Speak the sentence in your translation to understand the emotion:
then, once you have engaged with emphases and cadence, speak the original with that feeling.
Repeat until you feel 'at one' with the feel of the words in your mouth.