In terms of the diaconate: 35 is the minimum age for Ordination, not reception onto the programme which can typically take 4 - 5 years part time. therefore start talking to the director of the Diaconate now for more personalised advice especially regarding the rules in your dioceses.
A candidate for the Diaconate should be someone who is already involved in active Lay ministry.
areas of particular importance are those that express the particular virtues that are specific to the order of the Diaconate:
Service & Charity
Teaching & Preaching.
These apply both on the altar and off the altar.
The Deacon will learn to be a Reader at mass, and will receive the formal office of Lector during his training (if not already received). After ordination he will read the Gospel at Mass, as an expression of his job as a minister of Charity. After Ordination he may also Preach the Sermon (subject to the wishes of his Priest).
He also bestows some liturgical blessings, including the sacramental blessings of Baptism, and receives the wedding vows from couples who are getting married and blesses them.
He is called in particular to prepare people for these and the other sacraments. - He is called to be a Catechist. A Teacher of the Word of God.
He is an Ordinary Minister of Holy Communion: He distributes Holy Communion to the faithful both at mass and brings it to the sick and housebound. During his training he will receive the order of Acolyte. This includes being and EMHC as well as the functions of Alter Server.
He is called particularly to be a minister of Charity, and to administer the churches efforts in this area.
To prepare for and discern this calling, a man should be looking for how and where the lord is calling him to be actively involved in Charitable works.
If the Lord is calling you to these areas of work, then that calling applies now... not in 10 years time after ordination. Look to see how you can express these types of ministry now.
Such ministries will help you discern your vocation.
If these area not the areas of ministry are not where you feel called, then you need to look at what ministries you do feel called to now.
These will also help you to discern.
Talk to you Parish Priest. Look at the appeals in the news letter for areas where your parish or local charities need volunteers.
Look at what local lay movements and 3rd order groups are active in your area. Are any of these things that you and your wife could get involved in?
Ideally the Deacons ministry should include his wife... does your wife agree with your desire to seek such ministry? both now and in the future? Would she commit to it and the training as well? Would she stand back and support you? Would she not want it or resent it? (as a minimum you must have her informed, written consent to apply to start the training, and again before ordination, but they (the selection teams) prefer her active involvement, and comittment to training for Lay ministry if possible... in my area the Wives go through the same training as their husbands... but as they are not to be ordained they are not subject to being kicked out of the programme if they don' make the required grades.)