"How do I easily locate a particular person within the larger tree, without trial and error?"--mavitale
Okay, you are talking about a box-chart display of a tree.
There are some tree-hosting sites running on TNG (The Next Generation) software, that can display up to 9 generations in a box-chart on a monitor, but then you lose most details (middle names, dates of birth/death and their places). These can be downloaded as .pdf files, too.
To give a little comparison, working back to my early 17th century ancestors is 12 or more generations, depending on the particular lineage. In most of a particular tree, the number of ancestors doubles with every generation (but in practice the actual number for my example is fewer than 2-to-the-12th-power, since most trees have 1st, 2nd or 3rd cousins who married, who share common ancestry). In one line I have 2nd cousins marrying, in another 3rd cousins married. If I knew who all of the ancestors were, there would still be more than 1000 people to display for just that time period. There is no way to fit all of that on one page or legibly on a monitor -- and to the best of my knowledge no tree-site has worked out a zoomable display to show the whole.
One solution is the "5 generation pedigree chart," where you can have and display the key vitals for each generation. The furthest-back persons on one chart each become the latest person on the chronologically next-further-back 5-generation chart.
The Ancestry.com Member Trees provide similar schemes for pedigrees. You can display each X-generation group on a separate tab, but unfortunately the earliest generation for each box chart omits dates and places. The Ancestry pedigree box-charts for member trees are not very useful tools, and they do not provide any useful "descendants of" box charts all in one place (the supposed 5-generation family view can not be set up to show only 4 generations of descendants of a given person or couple).
Do explore the message boards concerning genealogy software. The most popular ones that are supported currently by their developers are The Master Genealogist, RootsMagic and FamilyTreeMaker, but there are newer ones and some more limited ones that are available for free download. The Message Boards:http://boards.rootsweb.com/topics.software/mb.ashx
--You can get an idea from posts and discussions where there may be issues and problem areas.
For an idea of some useful forms used by genealogical researchers, check the free ones listed in the right column of this page (the Rootsweb home page): http://www.rootsweb.ancestry.com/