Wedding toasts symbolize the combined wishes of the near and dear ones for the married couple, blessing them with a great and full-filling life ahead.
The following do's and don'ts, though not exhaustive, can be of great help in charting out a good toast for the well-being of the newly wed couple.
The Do's Of Wedding Toasts:

For any best man wedding speech toast to be interesting, it must be innovative and not copied from elsewhere.
The best man must thoroughly research and gather facts about the couple - how they met, the equation that they share, their plans, common interests etc.
before he starts preparing the wedding speech.
Including the comments of the family members on how they feel about the union of the couple is a good idea!

The best man speeches must be rehearsed before the final delivery to avoid stumbling or making mistakes on the D-day.
A rehearsal would also ensure that the speech is just perfect and keeps the audience engaged throughout!

Wedding toasts should be intercepted with light humor and jokes not only to actively engage the audience but also to make it more appealing.

The best man wedding speech toast should also be pertinent to both the bride and the groom as a couple and should not only focus on just one of them as that would misbalance the content of the speech.
The speech should also be pertinent to all present at the festivity so that everyone understands what is being talked about.

The wedding toasts should be brief and relevant.
It is a good idea to end the toast with a happy and hopeful note that acknowledges the benevolent moment and wishes the couple a prosperous and bright future.

The Don'ts Of Wedding Toasts:

Do not include any swear words in the speech much to the angst of any of the family member present at the ceremony.

Do not make the speech so funny that the end result turns out to be ridiculous, much to the embarrassment of the couple.

It is a great idea to talk one's heart and deliver the best emotional speech possible.
However, at the same time, one must not talk for the sake of talking as one may end up being repetitive and eventually boring the wedding gathering.

Do not forget to thank the guests for their time and patience and the family of the couple for arranging the wedding festivities (in case the parents have paid for the wedding).
One must also not forget to thank everyone for the presents that they might have presented to the couple.

Do not drink too much before the speech delivery such that it becomes difficult to maintain one's composure before the gathering.
Remember that no one is interested in a mumbled speech that makes no sense!

Wedding toasts for the happiness and prosperity of the newly wed are a token of love and warmth that others bless them with; therefore, it is essential that the toast is chosen carefully for it to be preserved in the memory of the couple till death does them apart!