diff --git a/README_starter.md b/README_starter.md
index 416f505c..67a5a34c 100644
--- a/README_starter.md
+++ b/README_starter.md
@@ -14,6 +14,24 @@ This will report which dependency, if any, still needs to be installed and confi
 
 If all dependencies are present, it'll run `asdf` to install language versions.
 
+### Prerequisites
+
+If the preflight script reports any missing executables or you run into any other errors, here are the prerequisites for running the app. Check you have all of these installed.
+
+1. asdf, which manages package versions. We recommend [installing with the `git` method][asdf-install]. We also need plugins for the versions specified in `.tool-versions` (the preflight script will install these for you).
+2. Docker Desktop (community edition). You can download the Mac version from [Docker Hub]. It's a self-contained install.
+3. PostgreSQL, the database. This can be installed with [Homebrew][brew-pg]: `brew install postgresql`. Be sure to follow the post-installation notes to make sure PG is running: `brew info postgresql`. You can start it with `brew services start postgresql`.
+4. A few dependencies for installing languages:
+   - `autoconf`: [required][erlang-req] to build Erlang; `brew install autoconf`
+   - `gnupg`: [required][node-req] to verify NodeJS; `brew install gnupg`
+   - For Erlang, it's recommended to skip the Java dependency on macOS. Run this or add to your shell: `export KERL_CONFIGURE_OPTIONS="--without-javac --with-ssl=$(brew --prefix openssl)"`.
+
+[asdf-install]: https://asdf-vm.com/#/core-manage-asdf?id=install
+[docker hub]: https://www.docker.com/products/docker-desktop
+[brew-pg]: https://formulae.brew.sh/cask/postgres#default
+[erlang-req]: https://github.com/asdf-vm/asdf-erlang#osx
+[node-req]: https://github.com/asdf-vm/asdf-nodejs#install
+
 ## Setup
 
 Once you've finished preflight setup, run the setup script:
diff --git a/bin/preflight.sh b/bin/preflight.sh
index 92e7b1c1..5536a72e 100755
--- a/bin/preflight.sh
+++ b/bin/preflight.sh
@@ -26,6 +26,8 @@ print_success() {
 
 print_step "Checking prerequisites"
 
+check_executable autoconf # Erlang prereq
+check_executable gpg # Node prereq
 check_executable asdf
 check_executable docker
 check_executable psql
@@ -33,6 +35,11 @@ check_executable psql
 if [[ $check_failed = 0 ]]; then
   print_success "All prerequisites installed"
 
+  print_step "Installing asdf plugins..."
+  asdf plugin-add erlang
+  asdf plugin-add elixir
+  asdf plugin-add nodejs
+
   print_step "Running asdf..."
   asdf install