That's tricky. After all, if you find a buyer for your existing home, before you've found a new one, you may find yourself living out of a suitcase if convenient closing dates can not be negotiated. On the other hand, if you find your dream home before you've sold your old one, you may be faced with carrying two mortgages for a time.
So how do you manage? Easy. Do your homework and have a good idea about the neighbourhood and type of home you're looking for. Do an honest evaluation of your family's needs and budget.
Start your new home search before or when your existing home hits the market.
If you've found a home before you've sold your existing one, use "sale of your existing home" as a condition in your Offer. If you don't sell your house within a fixed period of time, you can choose not to go through with the transaction. This, however, is a difficult condition for many sellers to agree upon and you may find that you have to forgo your price negotiating power.
As a buyer with a "sold house" you will be in a better position to negotiate price.
Purchasing a home before you sell could be a risky strategy if you're counting on the proceeds from the sale.
If you've found a buyer before you've found your next home, use "purchase of a new home" as a condition when you sign back your Offer. Again, it will only be for a fixed time. Even if you have not found the ideal next house by the time the time period lapses, if you feel comfortable that there is a house out there for you, you may still wish to proceed with the Offer.