Find the below link for jQuery

http://www.codeproject.com/Articles/618484/Latest-jQuery-interview-questions-and-answers

CRUD operations using Jquery in MS CRM 2011

function onLoad(context) {

    var accountId = Xrm.Page.data.entity.getId();
    //ReadMethod("MostRecent");
    //deleteAccount("41FB760C-2C4B-E211-AB64-0800270618E2");
    //WriteMethod("SAI KRISHNA YADAV");
    //updateRecord(accountId, "AccountSet");

}

function ReadMethod(queryName) {
    try {
        // debugger;
        var serverUrl;
        //serverUrl = Xrm.Page.context.getServerUrl() + oDataQuery;
        var accountId = Xrm.Page.getAttribute("primarycontactid").getValue()[0].id;
        $.ajax({
            type: "GET",
            url: "http://test/CRM2011VM/XRMServices/2011/organizationData.svc/ContactSet?$select=FullName&$filter=ContactId eq guid'" + accountId + "'",
            data: {},
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            async: false,
            success: function (result) {
                //debugger;
                if (result != undefined && result.d != undefined && result.d.results != undefined && result.d.results != null) {
                    // for (var i = 0; i < result.d.results.length; i++) {
                    alert(result.d.results[0].FullName);
                    //WriteMethod(result.d.results[0].FullName);
                    //}
                }
            },
            error: function (res) {
                //  debugger;
                alert(res.responseText);
            }
        });
    } catch (e) {
        debugger;
        alert(e.Description);
    }
}
function WriteMethod() {
    try {
        var serverUrl;
        var serverUrl = Xrm.Page.context.getServerUrl();
        var ODATA_ENDPOINT = "/XRMServices/2011/OrganizationData.svc/AccountSet";
        // Define attribute values for the CRM object you want created
        var newAccount = new Object();
        newAccount.Name = "Samplee";
        newAccount.Telephone1 = "123";
        newAccount.Fax = "456";
        //Parse the entity object into JSON
        var jsonEntity = window.JSON.stringify(newAccount);
        //Asynchronous AJAX function to Create a CRM record using OData
        $.ajax({ type: "POST",
            contentType: "application/json; charset=utf-8",
            datatype: "json",
            url: serverUrl + ODATA_ENDPOINT,
            data: jsonEntity,
            beforeSend: function (XMLHttpRequest) {
                //Specifying this header ensures that the results will be returned as JSON.
                XMLHttpRequest.setRequestHeader("Accept", "application/json");
            },
            success: function (data, textStatus, XmlHttpRequest) {
                var NewCRMRecordCreated = data["d"];
                alert("CRM GUID created: " + NewCRMRecordCreated.AccountId);
            },
            error: function (XMLHttpRequest, textStatus, errorThrown) {
                alert("failure");
            }
        });
    } catch (e) {
        debugger;
        alert(e.Description);
    }
}
function deleteAccount(id) {
    // Get Server URL
    var serverUrl = Xrm.Page.context.getServerUrl();
    //The OData end-point
    var ODATA_ENDPOINT = "/XRMServices/2011/OrganizationData.svc";
    //Asynchronous AJAX function to Delete a CRM record using OData
    $.ajax({
        type: "POST",
        contentType: "application/json; charset=utf-8",
        datatype: "json",
        url: serverUrl + ODATA_ENDPOINT + "/" + "AccountSet" + "(guid'" + id + "')",
        beforeSend: function (XMLHttpRequest) {
            //Specifying this header ensures that the results will be returned as JSON.
            XMLHttpRequest.setRequestHeader("Accept", "application/json");
            //Specify the HTTP method DELETE to perform a delete operation.
            XMLHttpRequest.setRequestHeader("X-HTTP-Method", "DELETE");
        },
        success: function (data, textStatus, XmlHttpRequest) {
            alert("Record deleted successfully!!!!");
        },
        error: function (XmlHttpRequest, textStatus, errorThrown) {
            alert("Error while deletion – " + errorThrown);
        }
    });
}

function updateRecord(id, odataSetName) {
    // Get Server URL
    var serverUrl = Xrm.Page.context.getServerUrl();
    var newAccount = new Object();
    newAccount.Name = "Samplee";
    newAccount.Telephone1 = "123";
    newAccount.Fax = "456";
    var jsonEntity = window.JSON.stringify(newAccount);
    //The OData end-point
    var ODATA_ENDPOINT = "/XRMServices/2011/OrganizationData.svc";
    //Asynchronous AJAX function to Update a CRM record using OData
    $.ajax({
        type: "POST",
        contentType: "application/json; charset=utf-8",
        datatype: "json",
        data: jsonEntity,      
        url: Xrm.Page.context.getServerUrl() + "/XRMServices/2011/OrganizationData.svc/AccountSet(guid'" + id + "')",
        beforeSend: function (XMLHttpRequest) {
            //Specifying this header ensures that the results will be returned as JSON.
            XMLHttpRequest.setRequestHeader("Accept", "application/json");
            //Specify the HTTP method MERGE to update just the changes you are submitting.
            XMLHttpRequest.setRequestHeader("X-HTTP-Method", "MERGE");
        },
        success: function (data, textStatus, XmlHttpRequest) {
            alert("Updated successfully");
        },
        error: function (XmlHttpRequest, textStatus, errorThrown) {
            if (XmlHttpRequest && XmlHttpRequest.responseText) {
                alert("Error while updating " + odataSetName + " ; Error – " + XmlHttpRequest.responseText);
            }
        }
    });
}

Add the onLoad function in Form onload/onChange of any field..