Let’s address this early in the lessons as it’s one of the biggest challenges in stand-up, especially when you’re new. If you’ve taken the bullet point approach described in the first lesson, you have a big head start as you’re not desperately trying to remember every word.
Whatever approach you’ve taken, one of the major challenges is remembering what comes next. Here, using images can also really help. Vivid mental images are great for linking bits that have no obvious connection. For example, if you go from talking about zoos to housework, make a cartoon in your mind of a gorilla doing the washing up. That way whenever you start doing the zoo bit this image will come to mind and you'll always remember housework is next.
You can create a chain of images like this that take you the whole way through a set. This can be especially helpful with disconnected one-liners. Say your next gag after washing up is about formula one, then you can imagine the gorilla throwing plates at formula one cars as they zoom past. Then if the next gag is about Boris Johnson you could image one of the racing cars being sent out-of-control by the plates and knocking Boris off his bike. And so on. Then when you perform the set, the cartoon is unfolding in the background of your brain; the visual bit of your memory working quite separately from the bit that's dealing with words.
You could also try using the 'memory palace' technique. This is a similar approach but takes more commitment to set up, but for some people it really works. Choose a house you know well, walk through it in your mind's eye placing vivid objects as reminders of your set as you go through. Proper memory masters have, in their mind's eye, a huge baroque palace that they can stroll around at their leisure. In my case I'd choose my mum's house.
Let's say my first gag or bit of material is about chips. If my tour of the property starts in the front garden then I could imagine seagulls feasting on a discarded bag of chips in the garden. Then I open the front door and go into the hall, and there I place something that reminds me of the next bit of material. If it's about bouncy castles then you know what I'll imagine in my mum's hallway. And round the house I go. Sticking to a prepared route and making the things placed around the house as vivid as possible. Then, to remember the set, I retrace my steps. As with the cartoon method, this process can happen unobtrusively in the visual part of your brain without interfering with the stream of words.
If you do get stuck, remember to use the language of conversations rather than performance, such as: "what was I saying?” “Oh! I had something to say.” “What did I want to talk to you about?" rather than: "I've forgotten my lines," or “what comes next?”
As a last resort have a single card in your pocket with the headings of all your sections on. So, if you are completely stuck, you can get it out, have a quick look and put it back. Have a line ready for this. A good approach is to make a feeble attempt to apparently cover it up. For example:
What I want to talk to you about now is absolutely seared on my memory. (SURREPTITIOUSLY (& OBVIOUSLY) CHECKS THE CARD)
Just having it there is beneficial, even if you don't end up referring to it. The very fact of having it in your pocket will calm you down and make you less likely to forget. Stand-up isn't a demonstration of memory feats, so feel free to write your topics on your hand. This is such an accepted convention now you can definitely get away with it—on a Stewart Lee DVD the menu is a close-up of the topics of the show written on his hand. You can potentially have some fun with it too as many acts do, such as the nervous new act joking that their topics have been sweated away.
And don't forget if you go off on a tangent and forget where you were, just ask the audience to remind you. Someone will know.
A good preparatory exercise to aid your recollection of the act, is to write out each individual bit of material onto index cards as a few words or bullet points. Then put the cards—the content— physically in order, trying different sequences until you’re satisfied with the flow. Then number the cards. This physical process is both useful for trying out running orders of your material is and useful for cementing the sequence in your mind. Try it alongside, or instead of, a flow of cartoon images as described above.