best thing is to temporarily) copy/paste a thin part of the left/right-most part of the map and drag it to the other edge and use it as a reference for plotting the coastlines there.

the poles are more difficult due to the amount of distortion there there's a lot of back/forth involved in making sure the coastlines look right in other projections. the best thing (that i know of) is to use the NASA G. projector for this http://www.giss.nasa.gov/tools/gprojector/ (though link is giging me a 403 error - ?)