Most of the articles I have found say that try to keep focus but here I want to ask is what do I focus upon ?
My problems, my desires or just how do we keep focus without a subject to feed upon ?
And while meditating I have found my thoughts wander away and keep reminding myself by repeating mentally "no I am meditating, no I am meditating". Is that the right method ?
If you use any imagination, verbalisation, visualisation of any sort this is not the betitation what the Buddha taught us to do as you have to come out of any verbal fabrication. (Cūla Vedalla Sutta)
but the biggest question is when we say focus(in any other field apart from meditation) we understand it in general context as to improve our performance or invest ourselves more in that field but what does it mean in meditation, is it repeating a thought continuously in our head or something else ?
Mental repetition can create concentration but this is not the right type of concentration which will lead you to liberation though you can turn this type of contraction into the right type by developing awareness on the arising and passing of sensations pertaining to the absorption. This is a long winded road than the straight road where you develop the right concentration followed by wisdom.
While some other articles say watch the thoughts as they occur , I mean okay I could watch the thoughts that occur during a meditation session but then doesn't that seem a little contradictory ?
Any mental state (Citta) or content (Cetisaka) give arise to some feeling either pleasant, neutral or unpleasant. (Comprehensive Manual of Abhidhamma) Even thoughts are sensed or felt thought the mind sense door which re perceive and react resulting in these sensations. Hence what you can easily recognise is the sensations pertaining to the thoughts.
You are producing the thoughts and then you are seeing that occur so then actually we could guide our thoughts then, why does it then say stay and observe ?
You should anchor your mind on a chosen object so that your do not think hence creating metal fabrication. (Cūla Vedalla Sutta) But if your main drifts to thoughts or the past or fantasy 1st look at the thoughts in your body with full equanimity looking at their arising and passing. If you have any unpleasant feeling pay attention for a small duration until such sensation become neutral or pleasant, then continue with your chosen object. Ultimately you have to be equanimous to whatever sensation you experience realising its arising and passing nature. (Pahāna Sutta)
I know above I have asked my questions in a hodgepodge manner so let me sum it up succinctly:
What are we supposed to think during meditation or we do not need to think at all ?
Generally do we set timers for meditation sessions or do we get an intuitive feel that I can't focus or meditate any more for today ?
If you feel you cannot focus on meditation any more then whatever practice you are doing seems to be causing stress. This implies you are not practicing properly and natural progress of meditation you should experience more happiness, joy, zest, tranquility. ((Ekā,dasaka) Cetanā’karaṇīya Sutta, (Dasaka) Cetanā’karaṇīya Sutta). Maybes you should double check your practice.