The fiancé is a stranger (non-mahram) to his fiancée so it is not permissible for him to shake hands with her, look at her with desire, be alone with her or speak words of love to her, etc. Rather Islam only permits him to look at her when proposing marriage without desire or being alone with her, because that will lead to a lasting marriage, lest there be anything that he dislikes in her that he does not know about but that may be a cause of him being put off by her in the future.
What some people do, being lax with regard to their interactions with their fiancées and looking, being alone with them etc, is a great evil which should be avoided and warned against.
If the fiancée cannot control himself with regard to the things that we have mentioned, then it is better for him to do the marriage contract straightaway, or shortly after getting engaged, so that he will avoid falling into haraam. It is well known that the one who has done the marriage contract is a husband and everything that is permissible for husbands is permissible for him, but he should not have intercourse until his wife moves in with him, in accordance with custom and so as to avoid any negative consequences that may result if intercourse takes place before the consummation is announced.
There is nothing wrong with delaying consummation from the time of the contract, for a year or three months, depending on each partners’ circumstances. There is no specific rule in sharee’ah concerning this matter, rather it varies according to people’s circumstances. In the past the engagement, contract and consummation may all have taken place on one day, or it may have been done otherwise. The Prophet (peace and blessings of Allaah be upon him) did the marriage contract with ‘Aa’ishah (may Allaah be pleased with her) when she was six years old and he consummated the marriage with her when she was nine.
What matters is that you should avoid falling into haraam. Hence the one who cannot control himself during the engagement period should hasten to do the marriage contract.
And Allaah knows best.