We should never preach heaven and hell without preaching God and sin. Heaven is only heaven because God is there. Hell is so very terribly hell because it is the eternal experience of the consequences of our sin.
To preach heaven on its own is to be like a spiritual travel agent. A travel agent describes a place so as people are persuaded into buying a ticket to get there. It is all based upon emotionally persuading people that this is the best deal available and they need to go for it. That is what the preacher who just preaches heaven does. They present heaven as the ultimate holiday destination and a must to be enjoyed. This approach is never engaged in in scripture.
To preach hell without saying it as a place of judgement for sin is to be a scare-mongerer. We present the ghastliness of hell, and truly it is ghastly beyond what words can convey, purely as a means of frightening people. What we should do is present the ghastliness of sin before a holy God.
We may have very good motives in adopting the approaches just mentioned, after all we want people to be heaven bound and not hell bound. If these are not our motivations then there is no love in us and, in a sense, there is no humanity in us. However, good motives are not enough. Such approaches depend upon our rhetorical skills to entice to heaven or deter from hell.
Inherent in these approach is the tendency to depart from the scriptural portrayal of heaven and hell and engage in speculation in order to gain an effect. So we conjure up vile images for hell and virtuous images for heaven to achieve our ends.
The corrective is always to be rooted in scripture for our approach to these matters. So we preach God as wholly beautiful in all His trinitarian, Father, Son and Holy Spirit magnificence. The consequence of such preaching is the awareness that heaven is only heaven because God is there.
Similarly hell is presented as the just vengeance of God against sin. Hell is an understandable place when we realise how vile an offence and sin is against a beautiful all loving holy Lord God.
We must be careful that our emotions in preaching flow out of a heart in tune with scripture. So our passions for being in glory with the Lord flow as we appreciate our God and our passions of alarm and concern flow when we present the vileness of sin. Yes we should be emotional in preaching, passions should flow. But they flow not because we are great thespians, but because God, through the Word of God, has got a hold of us.
Anyone who has attended drama school can whip up a fervour as regards to heaven and hell. But, only the Spirit anointed preacher can bring people to appreciate God and his ways. And through that, by the Holy Spirit, to see life transformation.