The housing market is very tight in Geneva, as generally in Switzerland. You can be sure that any flat you will visit had already seen tenth of potential tenants, and this is true regardless of how the flat looks like.
As for Geneva, downtown, approximate monthly rents are :

• 5500CHF for a 6 rooms flat, ~150m², unfurnished,
• 2000CHF for a two rooms flat,
• 2000CHF for a furnished 30m² single-room flat,
• 1300CHF for a furnished room in a shared flat.

These rates may be scaring at first sight, but, on top of it, you will also have to add three rents for the deposit. What is more, for a full flat renting, you will have to sign a renewable one year contract, without any possibility to stop it before the term, otherwise you would have to pay the full balance.

So you have to be extremely patient, but also persuasive, in order to find a flat. The points you should insist on are the usual ones : incomes constancy, rapid move, but also, for a shared flat, how often you travel.
This is because the shared flat (or better sublease) are frequently asking to potential flatmates how often they will be away, for example they can even ask you to leave the flat 3 weekends a month.

Anyway, for your search, do not hesitate to use your personal or professional network, and use internet.

For rentings, you will find several agencies on a search engine :

• classified advertisements websites [1] [2] [3] [4],
• housing specialized websites [5] [6] [7],
• real estate agencies websites [8] [9],
• RSS feeds [10] [11].

For shared flats, visit and regularly check :

• http://www.easywg.ch/ [12], specialised site on which I highly recommand you to take an abonment (generally, you will find 50+ adverts on it),
• http://www.recherche-colocation.com [13] is an other specialized site, but it seems to have a lowest interest in Geneva (~5/10 adverts at the same time),
• Glocals [14], the reference for any new comer and expatriate, for personal ads as well as business reviews, but also any type of social activities, got a dedicated forum section[14],
• the dedicated group on CouchSurfing [15], on which adverts are regularly published.

Hints :

• NEVER send money for a reservation before you met the occupant – some people are posting offers asking for some money, and send photos and other false informations,
• in each previous links, you can register and receive upcoming offers by email, do not hesitate to do so,
• be dynamic, and call the people when it’s possible.

Good luck in your search, you will need it – as well as patience.