While I am a little familiar with it (I think I played a video game set in the world a few decades ago), I have never read any of the Discworld books. I think I may remedy that but was wondering where is the best place to start. Any suggestions if you have read them?
I would suggest either Guards! Guards! or Small Gods.
GG is the introduction to the guards, IMHO the best of the recurring characters and is a very good book in its own right. SG is probably the best standalone novel, if you don’t like that one, Pratchett is probably not for you.
here is a flow chart for each of the story lines. The Colour of Magic is the first book, but I agree that the Watch books are among the best.
You might want to start by reading a few early posts in this thread
I like to read them in order (the world evolves over time) but The Colour of Magic is definitely a weak intro to the series.
Guards! Guards! is a great suggestion, and Sam Vimes is my favorite Discworld character.
I also like reading in publication order, but if you do that, make sure to get at least three or four books in before passing judgement. Pratchett was definitely still learning how to do it for the first few. Not that they’re bad, but others are definitely better.
Alternately, you could start with Small Gods. It has relatively little link, continuity-wise, with any of the others, and is also one of the better ones.
Alternately-alternately, you could start with the juveniles. The Amazing Maurice and his Educated Rodents is also relatively disconnected, but it’s also probably a bit below average. The Tiffany Aching series, which starts with Wee Free Men, is very good, and does have some connection to the earlier Witches books, but not so much that you’d be totally lost without them.
It’s one of the weaker Discworld books, but part of the problem is that so much of it parodies or alludes to older fantasy literature that many readers won’t be familiar with (along the lines of Fafhrd & the Grey Mouser, Conan the Barbarian, the Dragonriders of Pern, etc.).
@colinfred’s recommendations are good ones, but if you’d like to try a “quiz to see which book the Librarian recommends for you”, see here:
And here’s a larger and, I think, updated version of the chart in @Scoobysnax’s link:
Another vote for Guards! Guards! or Small Gods, though IMO, the Witches series, starting with Equal Rites, is another strong storyline.
I appreciate the discussion so far and invite further opinions but I noticed the book Mort is only $0.99 on Kindle. Is that a good first book to try? Definitely can’t beat the price.
Sure. It isn’t in the middle of one of the branches (as seen in the chart). Not really one of the Greats, but not a bad one.
Just don’t start with Colour of Magic.
Probably the worst book he wrote and it was the first. Weak parody instead of satire like he wrote later.
I don’t think I’d call Colour of Magic the worst… I’d put it ahead of Unseen Academicals and Raising Steam (both written late in his life, as the Alzheimer’s was gaining strength), and I remember being pretty unimpressed with Pyramids, too, though I don’t remember much of that one. Still definitely not one of the greats, though.
I love Pyramids…
Me, too.
I agree with that but I would still start at the beginning. If I was reading all of the books I would want to see how the world evolved and his writing matured.
If was only going to read a few I would I read the Guard books.
Am I reading the chart correctly that Pratchett recommends starting with Sourcery?
(I wonder since no one else has mentioned it.)
I just wanted to add that I’m rereading my entire Pratchett collection again and relish the prospect. 
I think you have great advice already (personally I particularly enjoy a Sam Vimes story, so start with Guards! Guards!..)
Start with Good Omens.
If you like that, continue as you will.
Back in the day, English books were hard(ish) to come by here and I read the series in the order that I could beg, borrow or buy them
Later I read the whole series in order, at random and back to front. It all works.
My favorite is Witches Abroad, but I’m unsure if it really works as a standalone.
Ah, Good Omens, that well known Discworld book…
I recommend you ignore this advice. Good Omens is not set on the Discworld and is more Gaiman than Pratchett in tone. It’s good, but not a measure of how much you would enjoy Discworld.
Definitely Guards! Guards!. The two Rincewind books may as well be from another series - the writing is different, the whole feel is different.
Since I’ve read a ton, maybe I’ll start again at the beginning, though…