I did start out my sketching with pencil for the same impression above. However, my pencil works for sketchbook are in a very different way than you might expect; they are not for line works but rather the build-up of pencil strokes, shades and shadows of objects. I will cover the subject of pencil sketching later on but it is the sketching with pen that I would like to start with for sketchbook.
Pens provide a simple continuous lines that are clear, uniform and most importantly, predictable. In other words, what you do is what you see and get; there’s no surprise, no technique required, no great skill needed and no tears! It is easy to produce or draw, easy to control. In sketching, one has no chance to make a mistake with pen. There’s no way to erase an ink line, therefore, one does not make an incorrect line but what happens is you get an EXTRA line, just one more line in addition to what you might have intended to! If you draw a wrong line, you use THAT line, even if it is not what you have wanted to, or draw another line and even another line if you want, till you’re happy with it. And no one would really mind ALL the lines you produced at the end.
Available types of pen for sketching.There’s many type of pens to choose from. What you would expect from a good sketching pen is probably the ink line that flows evenly, steadily to encourage the uninterrupted hand movement. In my opinion, the worst moment in ink sketching is when using a drying up pen! Beside the smooth flowing pen lines, you have the freedom of choice from line thickness, shape, size, brand, etc. I don't stick to any particular brand but generally use the pigment ink type which is fade proof and water resistant with line thickness of 0.2 to 0.4. The waterproof type ink allow for a cleaner sketch when wash-over with watercolor although sketches with water mark smears from the non-waterproof ink can be interesting on its own merit, if handled appropriately.
I use all type of paper for sketchbooks as long as they are of reasonable thickness that allows sketching on both sides with ink. What one wants to avoid is when the ink seep through from the other side of a thin or low quality paper. Paper surface and texture might be taken into consideration. Both smooth and rough paper surface could be used successfully with ink and pen depends on the type of pen used and the nature of the subject. Rough surface (and usually thicker) paper, may not lend itself to small detail drawings well but is suitable if watercolor add-on is the intended end result. It is most sensible to use reasonably smooth surface paper for general sketches for its versatility. However, one should be careful with the very smooth or shiny paper surface as it might take longer time for ink work to dry or smudge easily.
On watercolor wash sketches, many of the common quality papers, to my surprise, do take watercolor reasonably well. Most of the thinner paper on average sketchbooks do wrinkle when applied with color wash but somehow, that very characteristic seems to add the rugged or casual feel to drawing. This is all about traveling or field work any way and that suit me well.