The word alleluia is Hebrew and basically means, “praise God.” It is used in the original Hebrew in our worship as a superlative expression of joy. Sometimes the letter “h” is added to the beginning of the word, most likely as a musical notation to emphasize the first syllable.
We tend to drop the use of the word alleluia in Advent and Lent. It is used most frequently during Easter season and Christmas. Recently bishops, it seems, like to yell it out at all times of the year but it's really not necessary, during ordinary seasons like Pentecost, to include it in the Gospel acclimation or the dismissal.
I like to add an exclamation mark to the alleluia, to emphasize its role as an expression of joy. Therefore, it is not to be whispered in worship, it is to be yelled. The same is true of amen. Amen is also a Hebrew word and is a declaration of affirmation, literally meaning, “so be it.” It needs an exclamation mark in worship because it ought to be yelled too. It doesn't mean “I guess so,” it means, “YES!”
So, on Easter Day and throughout Easter season let's say alleluia and amen the way they were meant to be said: loudly, boldly, with exclamation and as if we mean it.
Easter Day is the biggest Sunday of the year. It is a day to celebrate the resurrection of Jesus Christ and all that this great event means for us and for all of creation. The resurrection is the greatest expression of God's love: that Jesus would be humbled to the point of death and that God would raise him up on the third day. Nothing, not sin, not time, not even death can separate us from the love of God. Amen and Alleluia!