Update dev vm instructions

doc/developing-using-vm.md

@@ -1,13 +1,25 @@
 # Developing using the VM
 
-## Installing and running
+## Installing
 
 NB: this assumes you are running on the GOV.UK virtual machine, not your host.
 
 ```bash
 ./install # git fetch from each dependency dir and bundle install
 ```
 
+### Installing dependencies
+
+Clone the following repositories:
+
+* [imminence](https://github.com/alphagov/imminence)
+* [asset-manager](https://github.com/alphagov/asset-manager)
+* [govuk_content_api](https://github.com/alphagov/govuk_content_api)
+
+Then run `bundle install` for each application.
+
+## Running the application
+
 Run using bowler on VM from cd /var/govuk/development:
 
 ```bash
@@ -17,3 +29,47 @@ bowl smartanswers
 ## Viewing a Smart Answer
 
 To view a smart answer locally if running using bowler http://smartanswers.dev.gov.uk/register-a-birth
+
+## Troubleshooting
+
+### Ruby version error
+
+Check the available versions of ruby by running:
+
+```bash
+rbenv versions
+```
+
+If the required version of ruby is not available in the list, your virtual machine may be out of date.
+
+To update the GOV.UK virtual machine first pull the latest version of the [govuk-puppet](https://github.com/alphagov/govuk-puppet) repository, then run:
+
+```bash
+vagrant provision
+```
+
+### DNS cannot resolve host smartanswers.dev.gov.uk
+
+The vagrant-dns plugin may be missing, or may not have installed correctly.
+
+On your base machine, go to the [govuk-puppet](https://github.com/alphagov/govuk-puppet) repository and check the available vagrant plugins:
+
+```bash
+vagrant plugin list
+```
+
+If the vagrant-dns plugin exists, first uninstall it:
+
+```bash
+vagrant plugin uninstall vagrant-dns
+```
+
+Then install it again:
+
+```bash
+vagrant plugin install vagrant-dns
+```
+
+N.B. If the plugin was missing, you just need to follow the install step.
+
+Finally, restart vagrant by running `vagrant halt` followed by `vagrant up`.