Aiko-chan

It takes a lot more than just a synopsis and a bunch of written scripts, or perhaps concepts to start making a game. Amateur projects tend to have issues mainly because the lead creators, who will be in charge of the whole project and it's team are often either way too ignorant, or don't have enough actual starting knowledge to begin properly.
 
First endavours should always be very simple and unless you already worked as a professional (meaning you have some ammount of knowledge and skill regarding the field of your work - be it programming, writing, art or music/sfx), there's no chance you will ever create anything highly polished straight from the very start. Your work will be shit and that's actually how it's supposed to be - even though it won't look anywhere near like the "project of your dreams", it will be yours, it will get finished and might not even be as bad as you'd expected it to be in the beggining - people may even like it. Commited devs, who are skilled enough to pull most of the work by themselves have the highest chances of actually finishing something as amateurs/begginers.
 
A lot of people expects that others will hapilly jump into the work with them and do that for free. In fact, it does happen, but VERY, VERY RARELY. In most cases no one will ever want to work with you seriously and even if you will find someone motivated as you, you can't expect anything exceptional out of them, because only other amateurs will be willing to give such work a spin, as they are mostly looking for experience and won't expect any payment in most cases; professionals are out of the question. In the end, everything revolves around money. If you're willing to spend it on the development (in other words, do it in a legitimate "business" way), you can even hire those professionals (as long as payment will be satisfying), but projects of low overall quality have a very weak chance to garner their attention (they have their own standards as well and often need to keep them; they won't work for amateurs in most cases). In overall, that's the same as simply buying out studios and making them work for you.
 
Art and music remain very important factors in visual novel development. In best case, you will have an artist who's willing to work from the very beggining to the end and keep the overall artstyle consistent. Same goes for the music, although there's a bit more freedom available in it. Getting those two things perfectly is extremely difficult for begginers. Developers who tend to be artists have the highest chance of pulling it off properly; otherwise, it's hard to expect the artwork to be both of high quality and consistency with your own concepts.
 
The best idea to start is to write a short GVD (game vision document) where you simply put a short synopsis of the game along with any major features/points the game will have; Imagine you're trying to sell your game as a product - what things does it have, that would make it special/stand out among other visual novels? Is it a deep, involving storyline? If so, is it branched? Does it have beautiful character designs/graphics? Lots of event cg's? Does the storytelling method involve the text to appear in a typical fashion, or is it somehow different? Maybe your game has some additional gameplay elements mixed in? Simulation, or strategy perhaps? It's a bit more harder in case of visual novels, since they are all about the same thing - conveying a story to the reader - but that's the best part as well, since it actually makes things a lot easier to manage.
 
To sum up, if you're really serious about it, treat it with equal respect. Game designing isn't some sort of a child's play. If you're commited enough, you might actually get somewhere in the near future; otherwise it's best to stop wasting your time on daydreaming as it will only lead you to nowhere.
 
It's much more complicated on the other side, but let's just say this remains a bare minimum for anyone, who wants to make visual novels:
Being at least a writer with a bunch of published/finished works or scripts; it's much easier to create and plan a visual novel from scratch, when someone already has a finished manuscript, or at least a first draft of it. Being a productive artist with some sort of a project summary and finished concept art - character assets, event cg's, backgrounds, etc. bonus points for someone who's willing to take the lead, or work on the whole art department by itself (though it can become a real burden in overtime, especially when the project tends to grow much bigger than expected). Some sort of funding. It's not necesarilly needed and higly dependable on the overall scope of the project; small "dojin" projects are capable to get finished without any sort of funding. The lead creator/designer must be a reliable person with a broad range of different talents and at least minimum knowledge on game design and team management; it's not even a joke, if you want to actually finish something and do it in an "acceptable" ammount of time. It will take you years otherwise and you will have a very huge chance of failing.  
TL&DR:
Don't even try to dream about making vn's, unless you're prepared.