Start DICO. Hitting the spacebar or double-clicking on the frame sends it to the taskbar.
While reading in an application, select one or several characters and hit CTRL-C (hold down the
DICO pops up with all entries that contain your selection. Flip pages by clicking the big LEFT and RIGHT buttons, or with the left and right arrows on the keyboard, or with the mouse wheel.
When done, minimize again (spacebar or double-click); or simply switch back to your window (CTRL-tab).
The search is inclusive, meaning that you will get all results that include your search: be it in the headword, the pinyin or the English definition.
Right-click on the frame, go to the font menu. Adjust fonts and colors independently for Chinese, pinyin and English. Experiment to find your optimal setting.
Use the up and down arrows on the keyboard to go to previous or next search. Or right-click inside the frame and go to "history".
The history list is arbitrarily limited to 100 entries. When you navigate back to some entry, later searches are not lost: any new search is inserted at this place in the queue.
In the search field, enter Chinese, pinyin or English.
Pinyin must be numbered piyin, like "ni3 hao3". If you are uncertain of piyin tones, replace them by @. Ex: "ni@ hao@"
If you search an English word, you might want to use the word delimiters < and >. For instance searching on "pin" while give you results with "spin" and "pint" as well. Searching for "<pin" will give you "pin" and "pint" but not "spin"; searching for "pin>" will give you "pin" and "spin" but not "pint". Searching for "<pin>" will give you only "pin".
To quicly search for a word, simply type the pinyin, without tones, as a single word. Example: "pengyou".
This method is by far the most convenient to search for polysyllabic words, when you have heard them.
However, this will only give you words whose pinyin exactly matches this, while typing "peng@ you@" would give you all entries whose pinyin includes pengyou, like 男朋友.
In some cases, toneless pinyin may overlap with English, e.g. "pin". In that case fall back on more complex searches, like "pin@".
Complex searches can be performed from the search field. For the advanced student of Chinese, they give the edge that an electronic dictionary should have over a paper one: finding words when you only have an approximation of the pronunciation, finding idioms that you remember partially, etc.
Back then, it happened several times that I searched for a word and did not find it in the dictionary; while all the time it was there but written with a different spelling. Variant characters are numerous in (traditional) Chinese, and people do not always agree whether this or that character is correct in a given word.
So I created a list of variant characters (mostly from UniHan, with a few additions of my own), and the search is performed on all possible variant combinations.
If you get some odd results that do not seem to correspond to your search, the variant list is the culprit: that list is pretty extensive, the aim being to find as many results as possible. The spelling of Chinese words as given by the dict is correct and usually the most common one; it's for you to check whether the variant spelling you have encountered would be considered correct.
The bottom bar includes a "filter" toggle. When "on", entries are filtered through available filters.
So far only one filter is available: it filters out entries for persons and place names, based on their pinyin beginning with a capital letter.
Most of the time these entries are visual noise to me.