Do you know where the custom of toasting originated?
Leave it to the ancient Greeks for initiating the art of toasting. The Greeks began toasting as a good faith gesture. While toasting, hosts would take the first sip to assure guests that the punch wasn't spiked with poison, a common occurrence in those days.

The Romans discovered that a charred piece of bread, known as a piece of toast, mellowed the flavor of the wine being offered.

At the rehearsal dinner, the host should get the party started with a welcome toast before the 1st course is served. The rest of the toasts should occur after dessert to avoid interfering with the waitstaff. If it is a buffet and more casual, the host may do a welcome toast after guests have served themselves and follow with a toast to the bride and the groom. After the host, the father of the bride can stand, followed by attendants and any other guests who may wish to speak.
At the wedding, toasts are typically offered after the cutting of the cake. If you are doing a champagne toast, be sure all the guests have been served a flute. A common wedding trend is to forgo the champagne toast” since many just take a sip and it's not cost-effective. It is perfectly fine for guests to toast with whatever they are drinking at the time of toasting.
Since toasting is a highlight of the wedding reception, below are samples of toasts to help the best man and others on the wedding day. Remember your toast should last no longer than two minutes since the more you talk, the less people remember.
If you forget what to say, remember this easy formula: Start with a little story that conveys the essence of the bride and groom, say how it relates to the happy occasion and how your life has benefited from knowing them and end by wishing them well.

This toast is the only truly essential toast offered during the wedding reception with all others being optional. It is customary for the best man to reminisce a little about his friendship with the groom, relating an interesting story with humor but always ending on a serious note. The toast should be delivered with as much heartfelt sincerity as possible.
______(the groom), when you asked _______(the bride) to marry you, you made the best decision of your life. I have know you for _____ years and have never seen you happier than you've been since the day you found _____(the bride). I am glad for you, buddy. And ________(the bride), you didn't do so bad yourself! What an awesome couple! May the happiness within your hearts today be with you forever in the years ahead and may all your dreams come true. Here's to ______ and ______.

After the best man and maid of honor has toasted, the father of the bride as host may wish to thank the guests, groom's family and friends.
Here is a sample:
I would like to propose a toast to all of you, our honored guests and especially to _______(the groom's) family and friends. What a splendid day this has turned out to be--everything has gone so well, even the weather cooperated and it has been such a happy day for all of us. ________(the bride's mother) and I would like to thank each of you for coming to help us celebrate the marriage of our beautiful daughter ________(the bride) and our handsome, new son-in-law________(the groom). We have known quite a number of you for years and others we have met for the first time today, and we thank you all for coming. I toast you all!

If the Father of the Bride chooses not to speak, the groom may thank the guests for coming to the wedding celebration. He may also want to toast the bride which should be short, poignant and well thought-out in advance.
Here is a sample:
What an honor to have so many special friends and family members celebrate this occasion with ________ (the bride) and myself this evening. We want you all to have loads of fun tonight...enjoy the music and great food and want to see each of you out on the dance floor.
On a more serious note, today I married my best friend. To my wife.