While some great ideas have been shared the reality centers on what your personal claims are as a performer. What would be excellent for a magician may not be appropriate for a Mentalist and conversely an Escape Artist, so what are you?
There are several videos and books that cover this topic
There are likewise little gems that can be found in Hugard's Monthly and any number of publications.
If Mentalism is your mainstay that opportunities are nearly limitless!
Most that are diehards in mentalism strive to work clean and without device. This imposes a number of techniques that range for item force tactics (which can be used for telepathic revelation or premonition, mind control, etc.) to actual "demographic controls" like Progressive Anagrams and suggestion techniques.
My two favorite "physical" situations when it comes to improvisational mentalism are Muscle Reading and Billet work in that both allow you to work by total happenstance.
DO UNDERSTAND that you can likewise learn how to use what is available as a form of tool -- a variant to what you would traditionally employ. For an example, a simple tube of chapstick gives you a tacky wax that can be used in a way similar to magician's wax but you also have the cap that can be used for either a Thimble manipulation routine or as a (yes) TT (and if you really KNOW how to work a TT, using a white, odd shaped cap in this way will prove that fact... Vernon used to challenge people with a Chrome (Mylar) or bright florescent painted TT). Similarly, you can borrow a strand or two of wonderfully long black or brown hair from a nearby young lady (or even some of the Bikers I know), after all, hair was the original IT.
The most important thing is for you to invest as much time and practice you can muster, into developing your slight-of-hand skills with items other than playing cards and which go beyond coins of common size and shape. That means things such as cigarettes, cigars, small glasses, salt & pepper shakers, fruits, balls of various sizes (gold balls, tennis balls, etc.) and of course the typical lady's scarf, belts, neck ties and in some cases clothing stunts such as the old waist-coat escape.