Designing a game from scratch seems like a daunting task but there are a plethora of resources that are available today.
Where to even start?
Use a framework that already exists. There are a multitude of board games that never make it to market - don't worry about those. Start studying your favourite games and start taking notes on them. What are some of the features or mechanisms that you like? Your friends like? Or hate?
Once you have a good understanding of what works and what doesn't, you can start applying these attributes to your framework and then you can apply a theme.
Our first idea was perhaps a controversial game called RIOT, in which 2 teams (rioters & police) would face off against one another in a grid of city buildings. The game would end with all of the rioters in jail or with the city left burning. I'm still convinced that this could be a winner but I was nervous about the timing of social unrest in the US and consequently saved this for perhaps our third game to market.
Creating a theme is probably one of the more fun brainstorming activities part of the design process. You can literally make any theme you want but some themes will mesh better with your framework. Think of settling on a new island(Catan, 1995), developing the landscape around a French castle(Carcassone, 2000), investing in real estate(Monopoly, 1935), or becoming the top trader for the Maharaja(Jaipur, 2009). The theme we finally decided on was one of my favourite things in the world, having a big breakfast.
The original design of Big Breakfast was modelled after one of our house favourites Sushi Go!(2013) in which players would select a card and pass on their hand to the next player. Certain cards give you a set amount of points at the end of the round. It was light, fun(can be described as a warm up game) and can be played at any time really with a time commitment of around 20 minutes.
I essentially applied the gameplay of Sushi Go! to my theme of building a big breakfast and that became our first completed game design. The next step was to add features that made our game unique and more complex.
*BoardGameGeek Forums is the place to hang out if you want to explore game design. You can discuss everything from game mechanics, artwork, themes, contests - pretty much anything you can possibly think of game related. If you wan to see some of the games that is in the pipeline, definitely check this out.
**Kickstarter Tabletop Games is where you can see games that have been completed and are now looking for funding to get started. This is a great resource to see what kind of games are coming out and a great place to get inspiration. If you see a game you like, support the project! You will be one of the first people to ever play that game and have probably helped out a budding entrepreneur!!