Dokku is an extensible, open source Platform as a Service that runs on a single server of your choice.
To start using Dokku, you'll need a system that meets the following minimum requirements:
1GBof system memory 
You can optionally have a domain name pointed at the host's IP, though this is not necessary.
Dokku is designed for usage on a fresh VM installation, and should install all necessary dependencies if installing via the bootstrap method.
To install the latest stable version of dokku, you can run the following shell commands:
# for debian systems, installs Dokku via apt-get wget https://raw.githubusercontent.com/dokku/dokku/v0.10.4/bootstrap.sh; sudo DOKKU_TAG=v0.10.4 bash bootstrap.sh
The installation process takes about 5-10 minutes, depending upon internet connection speed.
If you're using Debian 8 or Ubuntu 14.04, make sure your package manager is configured to install a sufficiently recent version of nginx, otherwise, the installation may fail due to "unmet dependencies" relating nginx.
Once the installation is complete, you can open a browser to setup your SSH key and virtualhost settings. Open your browser of choice and navigate to the host's IP address - or the domain you assigned to that IP previously - and configure Dokku via the web admin.
Warning: If you don't complete setup via the web installer (even if you set up SSH keys and virtual hosts otherwise) your Dokku installation will remain vulnerable to anyone finding the setup page and inserting their key.
Once you save your settings, the web admin will self-terminate and you should be able to run or deploy to the Dokku installation.
For various reasons, certain hosting providers may have other steps that should be preferred to the above. If hosted on any of the following popular hosts, please follow the linked to instructions:
As well, you may wish to customize your installation in some other fashion. or experiment with vagrant. The guides below should get you started: