Buying Tickets

I'm getting close to the point where I'm thinking about buying my plane ticket. Unfortunately, I'm stuck trying to figure out what type of ticket to buy. It looks like most round trip tickets are only marginally more expensive than a one-way ticket, so it seems stupid to get a one-way ticket, even if I end up tossing the return ticket away. That said, it also seems strange booking a flight for a leg than I really have no idea if I'm going to use or even if I'll want to come back at that point.

I also haven't completely decided if I want to come back to BC briefly after the first trip, or simply carry on to the next place for a while (which is tentatively Paris at this point). So I'm debating buying that leg up front as well. While I've seen last minute specials for the odd vacation package, it's not very often I've seen reduced prices at the last minute for international flights, so I'm hesitant to put off buying a ticket until the last minute for cost reasons.

Anyone have any suggestions or recommendations?