Originally Posted by Solent-Salted
Any advice is welcome.
Keep the brown stuff on the right
OK it's a glib answer, but it's really all you need to do. It's not a difficult trip given a decent boat and some half decent weather. A bit of passage planning would be sensible, but don't get too bogged down - it's only 150 miles or so, with no major hazards.
Once you're past the Needles you've only got St Alban's Head, Portland Bill and Start Point to interrupt a straight course all the way to Falmouth. Lyme Bay can be challenging in a stiff wouthwesterly, but if you're sensible with the weather it shouldn't be a problem. A copy of West Country Cruising by Mark Fishwick has lots of good information and is a good investment.
It's easily doable in a day, but you'll be passing a lot of good places so why not take in a few of them. You've already identified Weymouth as a stopover, but you might like to add Dartmouth or Salcombe, them maybe Fowey before heading on to Falmouth. There are plenty more options if you decide you really want to explore - if you want to go somewhere slightly less obvious how about West Bay or Lyme Regis?