The fiscal cliff bill signed shortly after New Year's provided a permanent extension of the portability of the unused portion of a spouse’s lifetime gift and estate exclusion amount ($5.12 million in 2012 and indexed for inflation thereafter). This provision gives couples an additional way to preserve both spouses’ full exclusions without the need for traditional credit shelter and bypass trusts. In other words, a couple can combine their $5 million (indexed) exclusion when elected after the first spouse's death. This was already the case for 2011 and 2012 but was extended on a permanent basis.
If you are married and especially if you have kids, consider establishing a living trust. You are the trustee as long as you are alive and your spouse becomes the trustee if you pass away. If both you and your spouse pass away at the same time (perhaps in an unfortunate accident), you designate who the trustee will be. The whole purpose of this is to avoid having all your assets go through probate upon your death. The trust is the owner of the assets and they can then be given out to your designated beneficiaries upon your death. Probate is a long and costly process that should be avoided when possible.
You will probably want to pay a lawyer to get everything set up for you and he or she can also assist with the transfer of any real property (real estate) into the trust. It is then up to you to move all of your bank and investment accounts into the name of the trust. This might seem like a hassle, or even strange, to have checks written with the name of your trust on them rather than your name, but it will be worth it.