I have read numerous hadeeth that greatly encourage Dhiker(Ziker). The prophet said that the only regret that the people of paradise will have is not doing enough of it.
There are many statements (given in the Hadeeth) glorfying Allah and praising Him and acknowledging his power over us. I understand enough Arabic for me to be able to understand most of these statements, and so when I'm saying them in Arabic, their meaning is not lost on me. However sometimes when I'm doing this Dhiker for a long time, my mind tends to wander and I can no longer concentrate on the meaning and implication of the statements I'm saying. When my mind wanders this way , I tend to think that my Dhiker is ineffectual, and that I'm just wasting my time.
Do I have to concentrate on the meanings of the statements everytime I say them? It becomes difficult to do so because sometimes I do Dhiker for a long time, and that kind of forced attention is beyond me.
Please tell me what exactly constitutes Dhiker. I don't want to have any regrets in Paradise (if I ever get there!).
You have rightly stated that we are required to remember the Almighty and remain constantly conscious of his innumerable favors upon us. This remembrance should primarily be through His attributes, as we know Him only through His attributes. We are told to remember him in context with his favors and blessings. For example we should say 'Al hamdu lillah' (All praise be for Allah) whenever we realize or are reminded of any of His favors upon us. We should seek His forgiveness for our mistakes and imperfections, whenever we are reminded of His perfection and our mistakes and sins.
We should try to remain conscious of our Dhikr. However, sometimes we lose track of the meaning of the words that we utter with our tongue, as you have experienced. This is likely to happen with humans because they are bound to be involved in their worldly affairs, concerns and thoughts.
Dhikr actually means remembrance. Our remembrance of God should ideally emanate from a conscious mind that has realized or is reminded of God's grace, justice, providence, omnipotence, omniscience and wisdom and then flow from our tongue - in the shape of words of praise and glorification in any language - and from our body - in the shape of actions that are pious and coherent with the requirements of these attributes of God.