How to write MongoDB query in Meteor?

How to write MongoDB find query in Meteor?

Or 

How to write MongoDB update query in Meteor?

First of all find query 

Select symbol.yahoo from user where active='true'

user.find({active:true},{fields:{'symbol.yahoo':1}});

Update query in MongoDB Meteor

update user set open_at=9pm and trade_date ='2012-12-20' where symbol.yahoo='meteor'

 var updata = {

            open_at : '9pm',

            trade_date : '20122-12-30'

}

user.update({'symbol.yahoo':'meteor'}, {$set:updata});